Researchers at the Department of Forensic Medicine and Toxicology at the All India Institute of Medical Sciences in New Delhi, together with a colleague from the Department of Biochemistry at Vardhman Mahavir Medical College and Safdarjung Hospital, analyzed 247 autopsy-confirmed natural deaths. The team, led by Gokul G., Abilash S., and Abhishek Yadav under the supervision of Sudhir K. Gupta, deliberately excluded cases with trauma, visible putrefaction, or invasive airway management. Each of those exclusions matters: trauma can introduce air into vessels artificially, putrefaction generates gas that swamps any earlier signal, and procedures such as intubation or resuscitation can push gas into the circulation. By stripping away these artifacts, the researchers could study intravascular gas in its cleanest possible context, the early postmortem interval in bodies that died naturally.

The technical approach was straightforward but rigorous. On pre-autopsy PMCT scans, the team graded intravascular gas on a scale from zero to three in three vascular territories: the hepatic vessels serving the liver, the coronary vessels supplying the heart, and the cerebral vessels of the brain. Grading rather than simply noting presence or absence allowed the researchers to test whether the amount of gas increased with time since death, as a decomposition-driven process would predict. Statistical analyses then evaluated two distinct questions: whether gas grade correlated with the postmortem interval, and whether gas in one vascular system was associated with gas in the others.

The results were striking. Gas appeared frequently in the hepatic vasculature, present in 50.6 percent of cases, and in the coronary vessels, present in 51.4 percent of cases. But the cerebral vasculature told a very different story: gas was found there in only 9.7 percent of cases. This asymmetry alone is informative. If intravascular gas were simply a uniform decomposition product diffusing through the entire circulatory system, one might expect it to appear more evenly across territories. Instead, the liver and heart vessels filled with gas roughly half the time while the brain’s vessels almost never did during the early postmortem period.

Even more consequential was what the correlation analysis revealed, or rather failed to reveal. Across all three vascular territories, there was no significant linear correlation between gas grade and the postmortem interval. In practical terms, this means that the amount of gas visible on PMCT cannot serve as a reliable clock for estimating time since death, at least during the early postmortem window this study examined. That finding challenges a line of research that has sought to use postmortem gas volume changes for postmortem interval estimation, including animal-model studies and investigations linking gas detected on PMCT with hypostasis and the postmortem interval. The new data suggest that during the critical early hours, gas accumulation does not progress in a predictable linear fashion that forensic investigators could convert into a time estimate.

But if gas is not a clock, what is it? The answer, according to the study, lies in its distribution pattern. The researchers found a strong systemic association between the hepatic and coronary systems, with a correlation coefficient of rho equal to 0.765. In other words, when gas appeared in the liver’s vessels, it very often appeared in the heart’s vessels as well, and vice versa. The two systems filled together, suggesting a shared underlying mechanism rather than independent local processes. This tight coupling between the portal venous system of the liver and the coronary circulation echoes earlier observations, including PMCT demonstrations of the relationship between gastrointestinal distension and hepatic portal venous gas, and analyses of cardiovascular gas in non-traumatic deaths.

The cerebral vasculature added a final layer of pattern. Cerebral gas was observed only in conjunction with hepatic and coronary gas, and isolated cerebral gas was never identified in the entire sample. The brain’s vessels, in effect, only filled when the liver and heart vessels had already filled. This hierarchical pattern, hepatic and coronary gas common and coupled, cerebral gas rare and dependent, gives forensic radiologists a reproducible systemic signature for early postmortem intravascular gas in natural deaths.

That signature has immediate practical value. When a PMCT scan shows gas distributed in exactly this way, common in the hepatic and coronary territories, rare in the cerebral circulation, and never isolated in the brain, the finding is consistent with a normal postmortem process in a natural death. Conversely, a deviation from the pattern, specifically isolated cerebral gas on PMCT, stands out as anomalous. The authors hypothesize that such findings may indicate antemortem etiologies, such as air embolism or barotrauma, in which gas entered the circulation before death and became trapped in the cerebral vasculature. This hypothesis requires future validation, but it offers a concrete, testable rule for a distinction that has long troubled forensic interpretation. Prior work has grappled with exactly this problem, including case reports differentiating putrefactive gas from air embolism in traumatic carotid-jugular arteriovenous fistula, scoping reviews of medico-legal interpretations of gas on postmortem CT, and evaluations of gas at PMCT in non-putrefied trauma and non-trauma cases. Intracranial gas on postmortem CT in traumatic cases has been particularly contested in medico-legal opinions, and gas analysis has even been used alongside postmortem imaging to diagnose causes of death through compositional analysis of the gas itself.

The study’s design choices strengthen its conclusions. Ethical clearance was granted by the AIIMS Institutional Ethics Committee, informed consent was obtained from the legally acceptable representative of each deceased person, and the work was conducted in accordance with the Declaration of Helsinki. The retrospective observational design, applied to a large consecutive sample of natural deaths with strict exclusion criteria, minimizes the confounding that has plagued smaller studies. The authors note no competing interests and no external funding, and the data generated for the study is available from the corresponding author on reasonable request.

For the growing field of forensic radiology, the implications are considerable. PMCT has become a standard component of virtual autopsy workflows since the early feasibility studies of postmortem multislice CT and MRI, and every scan raises the interpretive question of what intravascular gas means. This study provides a data-driven answer for natural deaths: during the early postmortem interval, intravascular gas follows a predictable systemic association across the hepatic, coronary, and cerebral vascular systems, and it does not track the postmortem interval in any usable linear way. The pattern itself, rather than the quantity of gas, becomes the diagnostic signal. If future validation confirms the authors’ hypothesis, isolated cerebral gas on PMCT could become a recognized indicator of antemortem air embolism or barotrauma, transforming a frequent and ambiguous finding into a targeted clue for cause-of-death investigation. In the meantime, the study gives forensic pathologists something they have lacked: a reproducible baseline for one of postmortem imaging’s most common sights.

Subject of Research: Distribution of postmortem intravascular gas on PMCT in natural deaths

Article Title: Distribution patterns of postmortem intravascular gas on PMCT in natural deaths

Article References: G., G., S., A., Yadav, A., Kumar, P., K., K., & Gupta, S. K. (2026). Distribution patterns of postmortem intravascular gas on PMCT in natural deaths. International Journal of Legal Medicine. https://doi.org/10.1007/s00414-026-04041-3

Image Credits: AI Generated

DOI: 10.1007/s00414-026-04041-3

Keywords: PMCT, postmortem intravascular gas, forensic radiology, postmortem interval, air embolism, virtual autopsy, Distribution, patterns, postmortem, intravascular, natural, deaths

Estimating the PMI has always been part science, part art. Pathologists traditionally rely on the classic postmortem signs taught in every forensic curriculum: the cooling of the body (algor mortis), the purplish pooling of blood (livor mortis), the stiffening of muscles (rigor mortis), and later, the progression of putrefaction or the developmental stage of insects colonizing a corpse. Each of these indicators is heavily influenced by ambient temperature, humidity, clothing, body mass, and a hundred other variables. The result is that conventional estimates are often empirical and imprecise, and most methods are only reliable within roughly the first 24 hours after death. Because a precise time of death can narrow a suspect pool, validate or destroy an alibi, and define the scope of an investigation, forensic scientists have long sought molecular markers whose degradation behaves like a dependable clock.

RNA has been an obvious candidate, but also a problematic one. Messenger RNA, the workhorse molecule that carries genetic instructions to the protein-making machinery, degrades rapidly after death, shredded by the ribonucleases that pervade both living organisms and the environment. That instability can itself be informative—several studies have used mRNA decay to estimate early PMI—but it also makes mRNA a poor internal reference standard for quantitative work. MicroRNAs, which are shorter and tougher, have shown promise, yet their degradation is still influenced by tissue origin, cause of death, and temperature. What forensic researchers ideally want is a molecule that is abundant, tissue-specific, and stable enough to survive hours or days of postmortem enzymatic attack while still changing on a measurable schedule.

Enter circular RNAs. First discovered in 1976 in viroids, circRNAs are a class of non-coding RNA molecules in which the strand has been spliced into a covalently closed loop. Unlike linear RNAs, they carry no 5-prime cap and no 3-prime poly(A) tail, which makes them largely invisible to the exonucleases that chew up ordinary RNA from the ends. This closed-loop architecture confers remarkable stability and long half-lives. CircRNAs are also highly abundant and show exquisite specificity to particular tissues and developmental stages—and nowhere are they more enriched than in the brain. Previous work has shown that circular RNA transcripts in mouse brain are abundant, conserved, and mirrored by similar transcripts in human brain tissue, making cross-species comparisons feasible. CircRNAs have already been explored in forensics for body fluid identification, bloodstain age estimation, and forensic age prediction, but a rigorous, temperature-controlled test of their use in PMI estimation has been lacking.

The Chinese team, led by Binghui Song, Jie Qian, and colleagues under the supervision of Jingliang Cheng and Junjiang Fu, began by mining public databases—circBase, circBank, the Tissue-Specific CircRNA Database, GTEx, and NCBI—to find circRNAs whose host genes are highly or specifically expressed in brain tissue. Four candidates emerged: circRtn4, circAtp5c1, circBcas1, and circBrsk2. The researchers designed divergent primers that only amplify the back-splice junction unique to circular transcripts, confirmed each molecule’s head-to-tail structure by Sanger sequencing, and then measured expression across 13 mouse tissues. CircRtn4 showed its highest expression in the brain, exactly as the database predictions had suggested. Of the four candidates, circRtn4 (technically mmu_circ_0000250, a 2,418-base-pair loop formed from exons 2 and 3 of the Rtn4 gene) stood out as the lead candidate, not least because it has a conserved human homolog, circRTN4 (hsa_circ_0054598), sharing 81 percent sequence similarity.

To turn degradation into a clock, the team needed stable reference molecules against which to normalize circRtn4’s signal. They screened eleven candidates, including common housekeeping mRNAs, ribosomal RNAs, a mitochondrial mRNA (mt-co1), and the well-known circular RNA circCDR1as. The results were telling. At 25 degrees Celsius, conventional mRNAs such as Tbp degraded fastest, while 28S rRNA, circCDR1as, and mt-co1 retained roughly 58 to 59 percent of their day-zero signal after eight days, with half-lives of about 8.6 to 9.5 days. The 18S rRNA, though initially stable, declined too quickly after day four to be useful. At the harsher 35 degrees Celsius condition, circCDR1as itself degraded too rapidly, leaving 28S rRNA and mt-co1 as the reference genes of choice. The lesson is one the authors emphasize repeatedly: reference gene selection cannot be assumed but must be empirically validated for every tissue, species, and temperature.

The modeling itself was meticulous. Sixty-two BALB/c mice were sacrificed under approved protocols, and brain tissue was collected at defined intervals—at 0, 1, 2, 4, and 8 days postmortem at 25 degrees Celsius, and at 0, 12, 24, 48, 72, and 96 hours at 35 degrees Celsius, each in humidity-controlled incubators set to 50 percent relative humidity. Using both semi-quantitative RT-PCR, where band intensity on agarose gels is quantified with ImageJ and standardized against a known DNA control loaded on every gel, and quantitative RT-qPCR, the team measured the circRtn4-to-reference ratio at each time point. They then fitted linear, quadratic, and cubic regression models, comparing them not just by R-squared values but with more rigorous statistics: the Akaike and Bayesian information criteria, leave-one-animal-out cross-validation error, nested partial F tests, and standard residual diagnostics. Quadratic models were statistically supported for the 25-degree data normalized to 28S rRNA and circCDR1as, while linear models were favored for mt-co1 at 25 degrees and for both references at 35 degrees; cubic terms added nothing.

The validation step revealed both the promise and the limitations of the approach. When models were tested on mouse samples with known times of death, prediction errors varied substantially across models, references, and time points. Some combinations performed impressively well—for example, the mt-co1-normalized linear model at 35 degrees estimated a 24-hour PMI with only a 3.8 percent error, and several 4-day predictions at 25 degrees were accurate within about 10 percent. But early PMI predictions, especially at the 2-day mark, sometimes erred by 30 to 85 percent. In the RT-qPCR analysis at 25 degrees, only the linear model showed a statistically significant relationship with PMI. A general pattern emerged: the longer the postmortem interval, the more accurate the estimation tended to be, echoing a known strength of molecular PMI methods for later intervals where traditional signs have faded.

Crucially, the team extended the work into human tissue, albeit in a strictly exploratory way. Cerebral cortex samples from a single healthy male donor, collected with informed consent roughly three hours after death, were incubated at 20 and 25 degrees Celsius and sampled across intervals extending to nearly five days. The human circRTN4 degraded sharply around two days postmortem and then remained low, and quadratic regression equations fitted to the data yielded R-squared values above 0.95 at both temperatures. The authors are careful to state that this single-donor analysis constitutes a proof of concept only—it cannot account for the variation in age, sex, cause of death, and environment that real forensic casework would encounter—but it demonstrates that the mouse findings have a plausible translational path.

What makes this study notable is its candor as much as its ambition. The authors openly acknowledge that circRtn4 performed poorly at 4 degrees Celsius, that mouse age (16-week versus 9-week animals across the two temperature experiments) may confound the comparison between temperature conditions, and that semi-quantitative RT-PCR, though cheap and visually intuitive, has a narrower dynamic range than the RT-qPCR or digital PCR platforms that future casework should adopt. Their conclusion is measured: circRtn4 may serve as a molecular PMI marker in mouse brain under the specific conditions tested, and postmortem circRNA models must be built species-by-species and temperature-by-temperature. Independent validation in larger human cohorts and veterinary-relevant species is required before any courtroom application. Still, the image is compelling—a loop-shaped RNA molecule, untouched by the enzymes that destroy its linear cousins, quietly recording the passage of time in the sealed vault of the skull. If larger studies bear it out, that silent loop could one day give investigators what they have always wanted: a molecular answer to the question of when death occurred.

Subject of Research: Use of the circular RNA circRtn4 as a candidate biomarker for postmortem interval estimation in mouse and human brain tissue

Article Title: CircRNA circRtn4 as a candidate molecular marker for postmortem interval estimation in mouse brain tissues

Article References: Song, B., Qian, J., Fu, J., Xiang, Z., Lu, L., Zhou, T., Yang, L., Cheng, J., & Fu, J. (2026). CircRNA circRtn4 as a candidate molecular marker for postmortem interval estimation in mouse brain tissues. Frontiers in Veterinary Science, 13, Article 1941625. https://doi.org/10.3389/fvets.2026.1941625

Image Credits: AI Generated

DOI: 10.3389/fvets.2026.1941625

Keywords: circular RNA, circRtn4, postmortem interval, forensic science, RNA degradation, PMI estimation, brain tissue, RT-qPCR, biomarkers, veterinary forensics, molecular forensics, reference genes

Zapico received the honor on Friday, Sept. 25, during a ceremony in Tiernan Hall, the building that houses New Jersey Institute of Technology’s forensic science laboratories. The setting was fitting: rather than a distant banquet hall, the award was presented in the very spaces where her students learn to handle evidence, run analyses and interpret results. The presentation took place as part of National Forensic Science Week, an annual observance that highlights the role forensic science plays in the justice system and the professionals who make that work possible. Britton Morin, director of the Union County Prosecutor’s Office Forensic Science Laboratory, delivered the award on behalf of the Consortium of Forensic Science Organizations, a body that represents more than 21,000 forensic science professionals nationwide. The presence of a working crime laboratory director at the podium reflected the award’s emphasis on bridging academic training and professional practice.

Moments after accepting the honor, surrounded by students and colleagues from NJIT’s Department of Chemistry and Environmental Science, Zapico turned the spotlight away from herself and toward the people she teaches. “I am very proud of what you have accomplished, what you are doing and what you will accomplish,” she told her students. “You make me a better teacher every day. I learn from you — you’re supposed to be learning from me, but I learn from you, too.” The remark captured a teaching philosophy that colleagues and students describe as deeply reciprocal, one in which the laboratory functions less as a lecture hall and more as a working research environment where undergraduates, graduate students and faculty pursue questions together.

That philosophy was central to the citation read at the ceremony. “At the heart of Dr. Zapico’s teaching philosophy is a simple but powerful belief: Students learn best when they are actively engaged with science and understand its relevance to real-world forensic investigations,” Morin said on behalf of the consortium. “Her students do not simply learn forensic science; they practice it. They analyze evidence, test hypotheses, interpret results and communicate conclusions, gaining the skills and confidence needed to succeed as future forensic professionals. Perhaps the greatest measure of an educator’s success is the inspiration they leave with their students.” The statement reflects a broader movement in forensic science education away from purely didactic instruction and toward immersive, evidence-first training that mirrors the demands of operational laboratories.

Zapico’s own route into the field was anything but direct, and she has often said that this winding path shapes how she mentors students today. Growing up in Spain, she was inspired by the detective fiction of Agatha Christie and the Sherlock Holmes stories, but at the time there were few opportunities to study or train in forensic science in her home country. She instead studied biology and biochemistry, completed her doctoral studies in cancer research, and only later pursued formal forensic science training. Her first opportunity in the discipline came in forensic anthropology at the Smithsonian Institution, an institution with which she remains connected today as a research associate. “Becoming a forensic scientist was a difficult path. I encourage my students to take every opportunity they have here,” she said. “This award isn’t only about what I’ve accomplished. It’s also about what I can pass on to them.”

Since joining NJIT in 2021, Zapico has led the ForenBioS Laboratory, where she involves students at every level in research on emerging forensic methods. Among the lab’s central projects are new approaches to estimating age at death from skeletal remains, a problem with direct consequences for identifying unknown individuals in missing persons and mass fatality investigations. Her research portfolio also extends into forensic epigenetics, including the use of DNA methylation patterns to estimate age, an area of growing interest because chemical modifications to DNA change in predictable ways across the human lifespan. More recently, the lab has examined the molecular effects of smoking, vaping and exercise among young adults, connecting forensic molecular biology to pressing public health questions about a generation exposed to novel nicotine delivery products.

The students who filled the ceremony offered the most concrete evidence of her mentorship in action. Forensic science undergraduate Marlene Mohammed ’27 first met Zapico at NJIT’s Accepted Students Day while she was still a student at Clifton High School, and has since worked on three research projects in the ForenBioS Laboratory. One of those projects uses advanced spectroscopy techniques to study skeletal remains, with the goal of improving estimates of the postmortem interval — the length of time a person has been dead, one of the most difficult parameters to establish in forensic anthropology. Mohammed and Zapico are scheduled to present that research at the Eastern Analytical Symposium in November, a major meeting that brings analytical chemists and forensic scientists together. “I definitely wouldn’t have realized my passion for anthropology or serology without her,” Mohammed said. “She’s a multidisciplinary researcher, so I also saw the benefits of working with different sciences and collaborating with many scientists.”

Zapico’s mentorship has carried students into a wide range of forensic careers. Alumni from her lab now work in the Bronx District Attorney’s Office, including in its digital forensics laboratory, while Ph.D. student and Fulbright scholar Maria Castagnola, who also attended the ceremony, is applying DNA-based methods to help identify unknown human remains — a humanitarian application of molecular biology that echoes Zapico’s own work with international forensic organizations. David Fisher, director of NJIT’s Forensic Science Program, described Zapico as absolutely integral to the program, citing her supervision of undergraduate capstone projects and doctoral students as well as her involvement in the university’s Forensic Science Initiative. That initiative introduces local high school students to forensic science through hands-on coursework and laboratory experiences, extending the pipeline of future practitioners well before students arrive on campus as freshmen.

The educator award is the second major national recognition Zapico has received this year. In June she was inducted as a Senior Member of the National Academy of Inventors, an honor that acknowledged her contributions to forensic science research and innovation, particularly in translating laboratory discoveries into practical methods. Her broader career spans academia and international humanitarian work: before joining NJIT she directed a forensic science master’s program at Florida International University, conducted postdoctoral research at the Smithsonian Institution, and worked with the forensic unit of the International Committee of the Red Cross in Geneva, where forensic identification of missing persons carries profound significance for families and communities affected by conflict. For now, Zapico says she is focused on what comes next for her students. “To see how they advance in their careers is special — to see them growing as scientists and as forensic scientists — I think it’s the most rewarding thing for me,” she said.

Subject of Research: Recognition of forensic science education and mentorship in forensic anthropology and forensic epigenetics

Article Title: NJIT’s Sara Zapico named National Higher Education Forensic Science Educator of the Year

Article References: NJIT’s Sara Zapico named National Higher Education Forensic Science Educator of the Year. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: forensic science, Sara Zapico, NJIT, forensic science education, Consortium of Forensic Science Organizations, forensic anthropology, DNA methylation, forensic epigenetics, postmortem interval, mentorship, National Forensic Science Week, higher education award

The research team, led by Marianna Manali and Konstantinos Moraitis, analyzed 256 forensic cases discovered between 1999 and 2023 across diverse Greek landscapes. Of these, 62 exhibited clear signs of carnivore scavenging, while 194 showed no such evidence. The cases were classified based on tooth marks on the bones or characteristic patterns of destruction consistent with carnivore activity, with modifications from other animals such as rodents deliberately excluded. The scale of the dataset is significant because previous studies have reported scavenging in roughly 15 to 45 percent of forensic cases examined worldwide, yet systematic retrospective research of this kind remains scarce in Europe, where legal, ethical and religious restrictions have long forced scientists to rely on animal proxies such as pigs instead of actual human bodies.

The statistics reveal a striking geographic signature. Scavenged remains were recovered at sites with a mean population density of just 465 inhabitants per square kilometer, compared with 2,713 for non-scavenged remains — a difference that was statistically significant. Scavenged cases also occurred at significantly higher elevations, averaging 325 meters above sea level versus 156 meters for unscavenged remains. Most scavenged bodies were found in woodland areas, heathland scrubs and grasslands, while non-scavenged remains clustered in constructed and industrial habitats where human presence is pronounced. Large carnivores, the study notes, tend to avoid areas of high anthropogenic disturbance, a pattern confirmed by experimental work in Spain showing that carcasses placed in publicly accessible zones attracted far fewer large scavengers than those in restricted areas.

Perhaps the most intriguing pattern emerged from the Greek islands. While the Aegean islands accounted for 20.6 percent of non-scavenged cases, only 4.8 percent of scavenged remains came from there. The researchers attribute this to the island biogeography effect: smaller and more isolated islands support reduced species richness, with scavenger taxa such as the golden jackal severely constrained and large carnivores like the gray wolf entirely absent due to geographic isolation. Tourism-driven development has further reduced the undisturbed open land where remains could lie exposed to wildlife. Coastal proximity, however, played no protective role — canid scavengers including feral dogs, jackals and foxes are well-documented coastal foragers undeterred by the sea.

The study also quantified how scavengers reshape the skeleton itself. Using a four-tier scoring system across 21 anatomical regions, the team calculated composite completeness scores and found that scavenged remains consistently showed lower preservation. Most strikingly, the upper limbs — the humeri, forearms and hands — were significantly less complete in scavenged remains, while lower limbs showed no statistically significant difference between the two groups. This pattern directly supports the classic disarticulation sequence described by William Haglund from canid scavenging in the Pacific Northwest, in which the ventral thorax and upper extremities are targeted first, followed by lower limbs, then progressive disarticulation of the vertebral column. Upper limbs are rich in muscle and connective tissue, rarely protected by heavy clothing, and their shallow glenohumeral joints detach far more easily than the deep socket of the hip.

The microscopic geography of tooth damage proved equally predictable. In the cranium, destruction concentrated on the occipital condyles, mastoid processes and zygomatic arches, with the mandibular rami highly susceptible. On the scapula, the acromion, coracoid process and inferior angle were typically destroyed, sometimes leaving only the scapular spine behind. The pelvis lost the iliac crest, ischial tuberosity and pubic symphysis first, and in extreme cases only the acetabulum survived. In long bones, both proximal and distal epiphyses were affected with nearly equal frequency — regions rich in fragile trabecular bone that gives scavengers access to the nutrient-dense marrow inside. Bone loss, the study found, was a more frequent modification than discrete tooth marks, which appeared most often as punctures on the iliac crest and femoral head.

Timing matters enormously. Nearly all scavenged remains — 98.4 percent — were found exposed outdoors, since scavengers generally cannot access remains buried deeper than about 30 centimeters. Most scavenged cases were recovered within the first year after death and showed advanced skeletonization with remnants of dehydrated soft tissue, whereas most non-scavenged cases were discovered after more than ten years. The statistical analysis revealed something subtle: in non-scavenged remains, skeletal completeness declined steadily with increasing postmortem interval, but in scavenged remains this relationship broke down, becoming weak and non-significant. Scavenging, in other words, does not merely accelerate the natural loss of skeletal elements — it fundamentally rewrites the pattern of destruction, particularly during the first months after death, when the difference between the two groups was most pronounced.

The research also carries implications for trauma analysis, one of the most delicate tasks in forensic medicine. Tooth marks on bone can be mistaken for perimortem sharp force trauma or even gunshot wounds, and extensive scavenging can obliterate genuine evidence of injury. Interestingly, perimortem trauma was recorded in 30.6 percent of scavenged cases versus 12.4 percent of non-scavenged ones. The authors suggest a biological explanation: large carnivores such as canids and felids are behaviorally attracted to blood odor, including the volatile compound trans-4,5-epoxy-(E)-2-decenal, and blood may help them locate remains before insect larvae colonize the body and inhibit vertebrate feeding. The presence of injury, it seems, can actively draw scavengers to a body.

Because the study was retrospective, the exact scavenging species could not always be identified, but the morphology of the puncture marks suggests members of the canid family — gray wolves, golden jackals, red foxes and feral dogs, all of which roam Greece’s wild and peri-urban landscapes. Brown bears, wild boar, European badgers and beech martens are also capable scavengers in the region, and some case reports noted stray dogs in the vicinity of the remains. One remarkable indoor case involved fully skeletonized, commingled remains from an abandoned stone church, where the destruction of both epiphyses on most long bones suggested prolonged, undisturbed gnawing consistent with scavenger caching behavior.

For forensic investigators, the practical message is clear. When skeletal remains are missing upper limbs, show crushed diaphyseal edges or puncture marks on fragile trabecular regions, and were found exposed in rural, elevated terrain, vertebrate scavenging should be a leading hypothesis rather than an afterthought. Systematic surveying of the surrounding environment for drag marks, animal scat, game trails and scattered bones can then confirm the diagnosis and even identify the species involved. In a European context where such data are rare, this quarter-century of Greek casework offers forensic scientists a verified baseline for distinguishing the work of animals from the work of humans — a distinction on which investigations, and justice, can depend.

Subject of Research: Carnivore scavenging patterns on human remains in forensic anthropology cases from Greece

Article Title: Carnivore scavenging patterns in terrestrial contexts: a 25-year retrospective study of forensic anthropology cases from Greece

Article References: Manali, M., Karydi, C., Spiliopoulou, C., & Moraitis, K. (2026). Carnivore scavenging patterns in terrestrial contexts: a 25-year retrospective study of forensic anthropology cases from Greece. International Journal of Legal Medicine. https://doi.org/10.1007/s00414-026-04029-z

Image Credits: AI Generated

DOI: 10.1007/s00414-026-04029-z

Keywords: forensic anthropology, taphonomy, carnivore scavenging, tooth marks, skeletal completeness, postmortem interval, Greece, canids, island biogeography, bone modification, decomposition, forensic science

The research team, led by Catarina Ermida of the Laboratory of Forensic Anthropology, together with Eugénia Cunha, Francisco Gil and Maria Teresa Ferreira, drew on a uniquely well-documented resource: identified skeletal collections in Portugal, including the 21st Century Identified Skeletal Collection at Coimbra and clavicles recovered from autopsies at the Portuguese National Institute of Legal Medicine and Forensic Sciences. Because the identities and death dates of these individuals are known with documented precision, the researchers could work with genuinely known postmortem intervals, something that is remarkably rare in this field. In total, 38 unburned human clavicles were analyzed, spanning PMIs from 4 to approximately 500 years. To probe the effects of heat, the team added a subsample of 12 clavicles that had been burned and carried a PMI of only four years, providing a natural experiment in how thermal alteration reshapes bone mineral independently of time.

The technique at the heart of the study, X-ray diffraction, is one of the workhorses of materials science. When a beam of X-rays strikes a crystalline substance, the atoms scatter the radiation in patterns dictated by the regular arrangement of the crystal lattice. Bone mineral, a poorly crystalline form of calcium phosphate closely related to the mineral hydroxyapatite, produces characteristic diffraction peaks. Freshly formed bone contains many small, imperfect, strain-laden crystals, and their disorder broadens and smears the diffraction peaks. As bone ages, and especially as it is altered by the burial environment, crystals tend to recrystallize and coarsen: small crystals dissolve and redeposit onto larger ones, lattice defects are repaired, and the peaks become taller, narrower and sharper. Two parameters capture this maturation. The crystallinity index, or CI, is calculated from the relative sharpness of the diffraction pattern, essentially a ratio comparing the height of key peaks with the depth of the trough between them. Crystallite size, meanwhile, is estimated from the broadening of the diffraction peaks themselves, using the physical principle that smaller crystals produce wider peaks. If bone mineral truly aged like a clockwork, both numbers should climb steadily with time since death.

That is roughly what the study found for the crystallinity index, but not for crystallite size. Across the 38 unburned clavicles, crystallite size showed no consistent relationship with PMI at all; values fluctuated widely from sample to sample, swamped by variability that had nothing to do with elapsed time. The crystallinity index told a different story. It displayed a moderate positive correlation with postmortem interval, with a Spearman rank correlation coefficient of 0.587, a statistically significant result with a p value below 0.001 and a 95 percent confidence interval stretching from 0.194 to 0.810. In plain terms, older bones did tend, on average, to show sharper, more crystalline diffraction patterns, consistent with the long-standing picture of slow diagenetic recrystallization. For archaeologists sorting ancient from modern material, that trend is real and useful. But the confidence interval also reveals how noisy the relationship is, and the devil, as so often in forensic science, was hiding in the scatter.

That scatter is precisely what limits the forensic dream. The authors observed substantial overlap in crystallinity values within the forensic timescale, meaning that a bone dead for five years might produce a CI indistinguishable from one dead for twenty or thirty years. Samples with identical known PMIs returned markedly different crystallinity values, a pattern the researchers attribute to taphonomic factors, the full suite of environmental insults that a body experiences after death: soil chemistry, moisture, pH, temperature swings, microbial attack, roots, and drainage. Two skeletons buried for the same number of years in different microenvironments can follow very different diagenetic trajectories, so the mineral fabric they present to an X-ray beam reflects burial history as much as burial duration. In forensic casework, where the difference between a recent death and a decades-old one can determine whether a crime is prosecuted, that ambiguity is decisive. A method that produces overlapping values across the critical range cannot pin a date, only gesture at one.

The burned-bone subsample added a further warning. Heat is known to drive dramatic recrystallization in bone mineral: as temperatures rise during burning, the small bioapatite crystals grow, merge and reorganize, sharpening diffraction patterns dramatically. The 12 burned clavicles in the study, all with a PMI of just four years, showed thermal alteration of crystallinity that could, in effect, mimic the signature of much older remains. A forensic investigator who analyzed a burned recent bone and interpreted its high crystallinity as a sign of antiquity would be badly misled. Conversely, cremated archaeological material could masquerade as fresh if the thermal signature were misread. The study’s authors stress that thermal history must be recognized and accounted for before any crystallinity measurement is interpreted as a proxy for time, and their data demonstrate concretely how fire can scramble the clock that X-ray diffraction is meant to read.

None of this means X-ray diffraction is useless in forensic contexts. The technique is fast, relatively inexpensive, minimally destructive, and its parameters do track genuine postmortem change in bone mineral. The crystallinity index’s moderate correlation with PMI confirms that mineral maturation is a real, measurable phenomenon, and the study’s use of documented skeletal collections shows how such measurements can be calibrated against known truth rather than assumed ages. What the findings deflate is the more ambitious claim: that CI or crystallite size alone can deliver a precise postmortem interval. The results align with a growing body of literature that has tested physicochemical dating proxies, from earlier X-ray diffraction studies to spectroscopic approaches, and found the same recurring pattern, a broad correlation with time that dissolves into scatter exactly where forensic questions need resolution. The authors conclude that, although XRD-derived crystallinity parameters provide useful insights into postmortem changes in bone mineral structure, their application for PMI estimation remains limited.

There is a broader lesson here about how forensic science progresses, and it is one worth savoring. The temptation in a young and under-resourced field is to chase a single magic number, a lone chemical or crystallographic readout that solves the dating problem once and for all. This study, grounded in 50 human clavicles with known histories, shows why that chase so often disappoints: death does not happen in a laboratory, it happens in soil, in water, in fire, and in a thousand uncontrolled environments that each rewrite the bone record in their own way. The measured effect of time is real but entangled with the effects of everything else. Progress will likely come not from a solitary indicator but from combinations of methods, larger and better-documented reference collections, and models that explicitly incorporate taphonomic variables rather than wishing them away.

For now, the crystals in our bones keep their secrets stubbornly. They do grow and ripen after death, and a diffractometer can watch it happen. But between a fresh forensic case and a centuries-old skeleton, the crystalline clock runs at different speeds in different graves, and fire can knock its hands sideways entirely. The Coimbra team’s careful negative result is, in its way, as valuable as a breakthrough: it tells every future investigator exactly where the limits lie, and redirects the hunt for the forensic clock of death toward approaches humble enough to respect the chaos of the burial world. Until then, the question of how long ago someone died will continue to demand the oldest tools of all, careful context, cautious inference, and the accumulated judgment of forensic anthropologists who know that every bone tells more than one story.

Subject of Research: X-ray diffraction analysis of bone mineral crystallinity as a potential marker of the postmortem interval in human skeletal remains

Article Title: X-ray diffraction analysis of bone crystallinity and its association with postmortem interval in human skeletal remains

Article References: Ermida, C., Cunha, E., Gil, F., & Ferreira, M. T. (2026). X-ray diffraction analysis of bone crystallinity and its association with postmortem interval in human skeletal remains. International Journal of Legal Medicine. https://doi.org/10.1007/s00414-026-04020-8

Image Credits: AI Generated

DOI: 10.1007/s00414-026-04020-8

Keywords: X-ray diffraction, bone crystallinity, postmortem interval, forensic anthropology, human skeletal remains, crystallinity index, crystallite size, taphonomy, bone diagenesis, burned bone, time since death, International Journal of Legal Medicine

The conventional toolbox for estimating the postmortem interval, or PMI, has long relied on physical signs of decomposition: body temperature cooling curves, the onset and resolution of rigor mortis, lividity patterns, and in later stages, insect colonization and microbial succession. Each of these approaches has well-documented weaknesses. Ambient temperature swings, morgue storage, wrappings and encasement, and individual variation in physiology can all distort the timelines inferred from these markers. Researchers have even shown that rigor mortis can persist far longer than classic models assume when bodies are kept cold, and that maggot development continues during refrigerated storage, complicating entomological estimates. The result, as the review’s authors note, is that conventional methods are often compromised by environmental factors and variable preservation conditions, restricting their accuracy and practical utility.

Vitreous humor offers a way around many of these problems, and the reason is anatomical. The fluid is sequestered behind the blood-retinal barrier, a selective gatekeeper that tightly controls which substances pass between the bloodstream and the eye. Because of this isolation, the vitreous humor exhibits relative metabolic stability after death and resists contamination and bacterial invasion far better than blood, cerebrospinal fluid or tissue samples. It is also less susceptible to the postmortem redistribution of drugs and metabolites that plagues toxicological interpretation. These properties make it, in the words of the review, an optimal biological matrix for PMI estimation, one that can extend the effective time window during which reasonably precise estimates are possible.

The scientific pedigree of vitreous humor analysis stretches back more than a century, to structural studies of the gel in the 1860s, but its forensic career truly began in the 1960s. In 1963, investigators reported that potassium concentrations in the vitreous humor rise steadily after death, a finding quickly confirmed by parallel studies showing that the correlation could serve as a clock for the postmortem interval. The mechanism is elegantly grim: after circulation stops, cells lose their ability to maintain ion gradients, and potassium leaks from intracellular stores into the surrounding fluid at a roughly predictable rate. Later work added hypoxanthine, a breakdown product of ATP metabolism that accumulates as oxygen deprivation sets in, and showed that combining hypoxanthine with potassium and ambient temperature improves estimates further.

Beyond potassium and hypoxanthine, the review catalogues a rich cast of biochemical characters whose postmortem trajectories correlate with time since death. Sodium and chloride concentrations shift in patterns that have proven useful both for PMI estimation and for distinguishing saltwater drowning from immersion deaths unrelated to drowning. Calcium and magnesium rise as cellular membranes fail. Glucose, urea nitrogen, creatinine and uric acid provide complementary information, though glucose is complicated by the fact that it can be elevated in conditions such as ethylene glycol poisoning. Ammonium accumulates as proteins degrade, and has even been measured at crime scenes using microfluidic paper-based devices designed to bring thanatochemistry out of the autopsy suite and into the field. Free amino acids, lactate, and protein fragments analyzed by high-performance liquid chromatography and mass spectrometry round out an expanding analytical repertoire.

Historically, the mathematical treatment of these signals relied on linear regression equations, most famously the potassium-based formulas refined across generations of studies. These equations correct for ambient temperature, age and other covariates, and software tools have been built to make them accessible to practicing pathologists. Yet the underlying biology is not strictly linear. Electrolyte diffusion, enzymatic degradation, temperature-dependent reaction kinetics and individual variation all interact in complicated ways, and single-marker equations carry confidence intervals that can span hours or days. Flexible regression models and chemometric approaches have pushed accuracy further, but the review argues that the real leap forward comes from artificial intelligence.

Machine learning entered the field in earnest in 2002, when researchers paired capillary zone electrophoresis measurements of vitreous electrolytes with artificial neural networks to estimate the PMI, demonstrating that nonlinear models could capture dependencies that simple equations missed. Since then, the approach has gathered momentum. Neural networks and other algorithms have been applied to sodium and potassium data, to metabolomic profiles of ocular fluids, and to microbiome succession data from animal models. Recent studies combining the human metabolome with machine learning have reported substantially improved PMI predictions, and systematic reviews now document machine learning and metabolomics applications across multiple tissue types. The review emphasizes that these models do more than enhance predictive accuracy; they enable robust nonlinear time series analysis of the complex, interacting biochemical changes that unfold after death.

The authors’ forward-looking vision is a multimodal fusion framework that integrates multiple streams of information: vitreous electrolytes, hypoxanthine and lactate kinetics, amino acid and peptide degradation patterns, imaging data such as the postmortem changes visible in the eye on computed tomography, and contextual variables like temperature and body weight. By training machine learning models on such heterogeneous datasets, the framework would hedge against the weaknesses of any single marker while exploiting the complementary strengths of many. The review also points to enabling technologies that could make this vision practical at scale, including tandem mass spectrometry, capillary electrophoresis, electrochemical biosensors for hypoxanthine, and rapid field-deployable microfluidic devices. Such a framework, the authors argue, is poised to become an indispensable tool for PMI estimation in forensic investigations and medicolegal proceedings.

Challenges remain before the vision becomes routine practice. Machine learning models are only as good as the data they are trained on, and the forensic literature contains decades of measurements gathered with different instruments, protocols and populations. Standardization of sampling and analytical methods will be essential, as will validation across diverse climatic conditions, causes of death and antemortem physiological states, since factors such as pre-death hypoxia can independently elevate hypoxanthine levels. Interpretability is another concern; courts and defense attorneys will demand to know why a model produced a particular estimate. Still, the review makes a compelling case that the convergence of a uniquely stable biological matrix, a maturing analytical toolkit and powerful computational methods is transforming one of forensic science’s oldest quests. What began with a simple potassium measurement in the 1960s is evolving into a data-rich, algorithm-driven science of the dead, one in which the fluid of the eye may soon testify, with unprecedented precision, about the moment life ended.

The choice of vitreous humor over alternative biological matrices reflects a broader pattern in postmortem biochemistry, where researchers have explored pericardial fluid, cerebrospinal fluid, and even synovial fluid as potential sources of time-dependent markers. Each fluid has its own advantages and drawbacks. Cerebrospinal fluid, for instance, contains promising markers such as glial fibrillary acidic protein, neuron-specific enolase and S100B, but its biochemical composition can vary depending on the sampling site along the spinal column, a source of variability that complicates comparisons across studies. Pericardial fluid has proven valuable for metabolomic investigations and for detecting markers of antemortem drug exposure, yet it is more exposed to contamination and postmortem diffusion from adjacent tissues than the sequestered ocular environment.

Practical considerations also favor the eye in casework. Vitreous humor can be collected with a simple needle aspiration through the sclera, typically from both eyes, and the small sample volumes required are compatible with standard clinical biochemistry analyzers as well as more sophisticated platforms. The fluid’s clarity and low protein content reduce matrix effects in spectrophotometric and chromatographic assays, which is one reason potassium-based methods achieved early reproducibility. At the same time, forensic researchers have cautioned that sampling technique, the interval between collection and analysis, and storage temperature can all influence measured concentrations, underscoring the need for harmonized protocols.

Imaging-based approaches add a complementary, non-destructive dimension. Studies of postmortem computed tomography have documented progressive changes in the eye, and measurements of the radiodensity of vitreous humor and cerebrospinal fluid have been proposed as indicators of the time since death. Because such imaging can be performed before autopsy without altering the specimen, radiological markers could eventually be integrated alongside biochemical ones in the multimodal frameworks the review envisions.

The pursuit of a single universal formula for the postmortem interval has long been viewed with skepticism among forensic scientists, and this skepticism shapes the review’s argument for data-driven fusion. Rather than seeking one equation that fits all circumstances, the field appears to be moving toward context-aware models that weigh temperature history, individual physiology and multiple analytes simultaneously. If validated rigorously, such models would not replace the forensic pathologist’s judgment but would supply a quantified, uncertainty-aware estimate that can be communicated transparently in medicolegal settings, marking a meaningful shift in how time since death is established in practice.

Subject of Research: Postmortem interval estimation using vitreous humor biochemistry and machine learning

Article Title: From biochemical markers to machine learning: a review of postmortem interval estimation via vitreous humor analysis

Article References: Rao, M., Wang, C., Tian, Y., Tao, H., Liu, L., & Zeng, X. (2026). From biochemical markers to machine learning: a review of postmortem interval estimation via vitreous humor analysis. International Journal of Legal Medicine. https://doi.org/10.1007/s00414-026-03979-8

Image Credits: AI Generated

DOI: 10.1007/s00414-026-03979-8

Keywords: vitreous humor, postmortem interval, forensic science, machine learning, potassium, hypoxanthine, blood-retinal barrier, thanatochemistry, forensic toxicology, artificial neural networks, multimodal fusion, death investigation