When a highly probative crime scene sample gives “no results” for the standard human mitochondrial DNA or STR assays, what can be done? One question remains unanswered: is this a highly degraded human sample with unrecoverable DNA, or a non-human sample? The hair in the victim’s hand, the hair adhering to the undercarriage of a vehicle in a hit-and-run accident, and the hair in the back of a suspect’s pickup truck are all evidence samples that may shed light on what happened in a particular crime. For skeletal remains, unless anatomically recognizable bones are recovered from a burial site, the species of origin may be indeterminate, even though a missing person was believed to have been buried nearby. Extremely fragmented and degraded bones can also present an analytical challenge.

Animals whose DNA has been observed in laboratory casework.

For many cases, determination that a highly probative hair or bone believed to be human is actually from another species can be helpful, opening or closing off lines of inquiry in the case investigation. The general but unfortunate trend of reduced training of and availability of experienced hair examiners sometimes results in the submission of non-human or indeterminable hairs to the laboratory for DNA analysis. Figure 1 shows a range of variation in hair appearance found in fur-bearing species; although hair microscopy may be recommended prior to DNA analysis, this type of examination is sometimes beyond the practical scope of the individual laboratory or even the greater laboratory system.

Figure 1: Photomicrographs of hair shafts, for different species of mammals. Left to right: human, human, cat, deer, and dog.