Forensics 101: A New Technique to Pinpoint Time Since Death

One of the very first forensics posts on Skeleton Keys was about using decomposition to pinpoint the time since death for fleshed bodies. As we mentioned back then, there are some fairly precise ways to measure time since death in first hours following death, up until 24—48 hours post-mortem. But after that, things are much less exact. Needless to say, this can be a problem for investigators who are trying to pin down suspects who need to substantiate their whereabouts with an alibi. But if the best you can do is a 24 hour period, it can be hard for even an innocent person to list all their movements. And what if the investigators are looking at the wrong 24 hour period due to an inaccurate estimate? A more precise way to identify time since death after the immediate post-mortem period would be a welcome tool for investigators.

A team of researchers who recently published in Toxicology Research may have an answer to this dilemma. Their original study set out to examine the changes in 46 biochemical blood parameters to develop a reliable mathematical model to determine time since death. Using 20 normal human blood samples, drawn, aliquotted, and left to coagulate normally, they temperature controlled blood cooling to mimic the typical drop in human body temperature after death—from 37oC to 21oC, decreasing 0.5oC per hour. They then started a kinetic (in time) analysis of the properties of the blood including pH measurements, protein, lipid, enzyme, and electrolyte levels and activity. Of the 46 parameters, ­­­­10 were found to be statistically significant in estimating time since death: total and direct bilirubin, urea, uric acid, transferrin, immunoglobulin M, creatine kinase, aspartate aminotransferase, calcium, and iron. Using these markers, researchers suggest that investigators and forensic scientists will be able to much more precisely pinpoint the time of death out to 11 days after death.

While the results are promising, the authors outline future areas of study as these experiments were done in vitro (outside the body) and under very controlled circumstances. Samples from deceased individuals of known time must also be studied for corroboration. In addition, multiple variables must be considered such as age, gender, body mass, cause of death, and length and type of stress at the time of death. External factors may also play a part—environment and temperature, humidity or precipitation, clothing, or whether the body is buried or left out in the open and possibly infested with insects or consumed by animals. So while there is a lot of research still to do, it’s definitely a very solid starting point from which to launch further research opportunities. Perhaps in a few years, investigators will have a dependable way to identify the time of death of individuals, making their search for suspects a more informed process, hopefully leading to better conviction rates.

Photo credit: Costa et al. in Toxicology Research