Dendrochemical forensics as material evidence in courts: How could trees lie?

Abstract

The legal admissibility of scientific tools, such as dendrochemistry providing forensic evidence for criminal or civil cases, critically relies on the quality of fundamental and applied scientific research. The “Daubert” and “Frye” criteria that federal courts in the U.S.A use for determining legal admissibility requires publication of the scientific basis for the tool, and general acceptance by the scientific community. The field of dendroforensics is rapidly evolving, with new methods constantly being developed. In this manuscript we investigate how this dendrochemical evidence has been used successfully in the courtroom. The study of tree rings using physical anatomical and dendrochronological methods has been used as evidence in courts for over 150 years. From these beginnings in dendroecology dendrochemical and biological methods have matured enough to allow it to be used in forensic investigations, finding applications as a new independent line of evidence around the world, supporting cases involving murder, trafficking of protected species, and pollution crimes. We summarize some of the key applications of dendrochemistry in forensic cases and illustrate them with courtroom examples. The basic analytical methods discussed (e.g., PCR, GC-MS, LIBS, LA/ICP-MS, EDXRF) are all conventional. However, for findings to be relevant to judicial cases, the data is normally applied with additional lines of evidence gathered such as tree physiology and relevant statistics. This can allow us to gain more powerful data to help age date a specific event or to spatially identify a source material. The purpose of this article is to show how recent research has paved the way for the use of dendrochemical evidence in courts. It shows how dendrochemistry can be useful for forensic investigations including: murder cases, trafficking of protected species, and pollution crimes. The applications are illustrated by several summarized legal cases, but due to the confidential nature of some of these cases it was not always possible to provide full details or references.