Was There a Body in the Trunk? Volatile Organic Compounds in the Trial of Casey Anthony and the Evolving Search for a Chemical Profile for Human Decomposition
SMU Science and Technology Law Review, Vol. XIX, No. 3, Fall 2016
53 Pages Posted: 11 Mar 2017
Date Written: 2016
In the 2011 murder trial of Casey Anthony in Florida, the prosecution was permitted to introduce evidence regarding the chemical analysis of a carpet sample taken from the trunk of a Pontiac where the body of the victim, the two-year-old daughter of the accused, may have been placed. The air from a Tedlar® bag that held the carpet sample was subjected to a series of steps, including cryotrapping and Gas Chromatography/Mass Spectrometry (GC/MS), resulting in the identification of 51 compounds, of which 41 were, according to the prosecution’s expert witness, consistent with a human decomposition event because they had been listed in a human decomposition database that he and research colleagues had prepared for the FBI.
That database, however, has not been made public and was not released for consideration by the jury, the judge, or the defense expert witnesses at trial. Some of the 41 compounds were eliminated from consideration by the prosecution’s expert because such compounds are present in gasoline vapors, garbage and other items that either were or could have been in the trunk, leaving only 16 compounds consistent with a human decomposition event. This list was further reduced by comparison to a list of 30 compounds significant in human decomposition events, a list that appeared in a 2008 paper of which the prosecution’s expert was the lead author, leaving only 7 compounds, and 2 of these were eliminated because they were only present in trace levels. Thus, in the end, the prosecution’s expert based his argument that a body had been in the trunk on only 5 chemicals. Arguably additional chemicals could have been eliminated as not present in a positive control or as present at levels too high for a typical decomposition event. The trial judge denied a motion to exclude the evidence, finding that the technology used to isolate the 51 compounds with which the chemical analysis began had previously been held to satisfy scientific evidentiary standards. The judge failed, however, to consider whether the Frye standard for admission of scientific evidence should apply to any of the additional steps by which the original 51 chemicals were reduced to the 5 that the prosecution maintained were sufficient to indicate a decomposition event had occurred in the trunk of the car.
This paper describes the chemical analysis used, the compounds reported to be associated with decomposition events in other studies, the trial judge’s ruling on the motion to exclude this evidence, and the history of the Frye and Daubert standards insofar as they have been applied to comparative and statistical steps in the presentation of scientific evidence. The authors conclude that the testimony of the prosecution’s expert witness should not have been admitted. However, the authors also conclude that continuing research is producing more and more information regarding the chemical profile of human decomposition and will most likely reach a level where such evidence can satisfy standards for admission in criminal trials.
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