Statement on Pattern Recognition Techniques in Wildlife Forensics
by the Society for Wildlife Forensic Science
May 7, 2015
There has recently been widespread media coverage of wrongful convictions based on unscientific application of forensic techniques. Most notorious, perhaps, are cases involving individual matching of hair by examiners in the FBI Laboratory’s microscopic hair comparison unit. According to a Washington Post report, FBI examiners gave flawed testimony in 257 of 268 trials in which hair evidence was used against defendants. In these cases, hair examiners testified that they were able to match hairs collected from a victim or at a crime scene with the hairs of a particular suspect. Thus, they used microscopic characters of hairs for individualization. Such individualization based on the physical characteristics of human hair has now been discredited as unreliable.
Unfortunately, the inappropriate use of hair comparison for individualization has led to a misperception in the public, and even within the legal community, that all techniques based on visual comparison and pattern recognition are unscientific. In fact, when appropriately applied to class character analysis, such techniques are scientific, reliable, and indeed essential, forensic tools, particularly in wildlife forensics.
This misunderstanding stems in part from confusion around the word “identification” in discussions of forensic analysis. It is crucial to make the distinction between identification to a class or group versus identification to an individual. In all crime labs, many forms of class character analysis are routine and scientifically unchallenged, for example identification of drugs, fibers, and paint. Biological evidence in human forensics deals almost exclusively with a single species, Homo sapiens, and the question posed is which human(s) was/were involved in the crime. Therefore, when forensic analysis of human biological evidence results in an “identification,” as in “hair identification,” what is typically meant is that an individual victim or suspect has been identified.
Wildlife forensics, in contrast, is concerned with the thousands of legally-protected species that may be illegally killed or entered into the wildlife trade. In wildlife forensics, “identification” typically refers to taxonomic or species identification based on group, or class, characters, rather than identification of an individual specimen. Such species identification is the essential first step to verify that an evidence item represents a protected species.
Pattern recognition based on class characters has been the fundamental methodology for the classification and identification of plants and animals by biologists for centuries. Detailed descriptions of anatomical characters (including fur, for mammals) are the basis for virtually all species descriptions in science, as well as for taxonomic keys and field guides. The rise of genetic analysis in recent decades has provided powerful new tools and fresh insights, but for most groups of plants and animals, visual examination of class characters remains the standard technique for species identification, provided that the evidence retains diagnostic morphological characters, and the examiner has the required education and experience. Thus, examination of hairs taken from a wildlife evidence item (e.g., fur coat, tanned hide) can yield a reliable and scientifically valid identification of the taxonomic source of that item.
To assure that wildlife forensic scientists meet the highest professional standards, the Society for Wildlife Forensic Science has developed a certification program for examiners, as well as adopting a set of standards and guidelines for laboratory procedures. These include best practices related to individualization, or matching biological evidence to an individual source. In wildlife forensics, this is performed only with genetic techniques, and only when there is an extensive database documenting the genetic variability of the species in question. Using only rigorously validated techniques, and employing the most appropriate analytical method for each type of evidence, wildlife forensic scientists are able to identify the extraordinary variety of protected plant and animal species, and contribute to the preservation of the world’s biological diversity.
For further information on the Society for Wildlife Forensic Science and its programs, visit (www.wildlifeforensicscience.org).