The lab work comes in two stages: First, the crime scene DNA is profiled employing a few marker regions from the genome, and next, the lab [Veterinary Genetics Laboratory at the University of California Davis (VGL)] uses its own pet genetic database to calculate probability — how common is this particular pattern in the wider population? In other words, how likely is it that this hair could have come from any other dog or cat than the one linking the criminal to the crime?
In the case of [a] triple homicide in Indiana, a representative of VGL testified that the statistical chance that the feces sample on the shooter’s sneaker and the feces in the yard of the scene of the crime came from two different dogs was staggeringly low. In fact, it was one in 10 billion. And since there aren’t even close to 10 billion dogs in the entire country that meant the feces on the sneaker and the feces in the yard came from the same dog.
The first time pet DNA was ever used as evidence in court involved hair shed from a white cat named Snowball. (Owners of white cats are thinking “of course!”) Sometimes pets even take an active role in helping nab the perpetrators of crimes against their loved ones.
An attempted sexual assault case in Iowa in 1999 was solved largely because of dog urine. Though the victim could not positively identify her assailant, her dog could — by having lifted his leg on the tire of the man’s truck. DNA matching of dog and tire urine placed the man at the scene of the crime.