How investigators, scientists and lawyers use canine DNA to solve crimes.
Forensic science is not just for humans anymore. Today, law-enforcement officials apply forensics to cases involving animals — whether the animal is a victim, perpetrator or witness.
“Many people don’t realize that there is animal DNA,” says Melinda D. Merck, D.V.M., senior director of veterinary forensics in anti-cruelty for the American Society for the Prevention of Cruelty to Animals.
Merck frequently testifies as a forensic veterinary expert in animal-cruelty cases across the country. These cases involve animal hoarding, puppy mills, dog fighting and animal torture. Evidence collected from these crimes must be analyzed and interpreted by a professional who understands animals and their behavior.
“I’m usually brought in by the prosecutor’s office or by a detective,” Merck says. “I may be sent a case file that includes statements, veterinarian records and photographs to consult on or to serve as an expert witness. I also look at bones and skeletal remains for evidence of cruelty, trauma or dog fighting. Often, I’m brought in to perform a necropsy.” The evidence she finds varies with each case.
Merck also trains veterinary and law-enforcement officials on the use of veterinary forensics in investigating and prosecuting animal-cruelty cases. Her interest in this field evolved from seeing cruelty cases in private practice and from her work with various rescue and animal-control groups.
In 2006, Merck testified in a high-profile puppy-torture case in Atlanta. Two teenage brothers were on trial for torturing a puppy and leaving it in an oven to die. Merck proved that the puppy was still alive when it was tortured. The brothers were sentenced to a maximum punishment of 10 years in prison.
As with humans, each dog’s DNA is different. Animal DNA can be collected from fur, saliva, teeth, blood, urine and even chew toys. “On a fresh or live body, the cheek swab is the ideal place to get DNA,” Merck says. “Sometimes we don’t have that luxury. If the body is decomposed, we can get it from muscles or a tooth root.”
Elizabeth Wictum, director of the University of California Davis Veterinary Genetics Laboratory in Davis, Calif., says that saliva, urine and feces are more difficult to test because they don’t inherently contain DNA. “As those materials pass through the ducts or intestines, they pick up cells from the lining and that is what we test,” Wictum says. Blood is a good source, but despite what you see on television, hair is not because shed hair lacks the follicular material that contains the DNA needed for individualization.
“We can get another kind of DNA, mitochondrial, which is inherited through the maternal line, but that isn’t as powerful,” Wicturn says. “Sometimes, we get lucky because dogs and cats groom themselves and leave saliva on the fur, so now and then we get a DNA profile from shed hair.”
CSI in the four-legged world
UC Davis started the forensic division of the VGL at the urging of law-enforcement agencies. In the 1950s, the VGL performed parentage verification in cattle using blood typing. The lab performed this service on more species over the years, mostly for breed registries. In the early 1990s, the VGL switched to DNA testing because it had been successful in human parentage testing labs. Several police agencies contacted the VGL, asking them to apply their animal DNA tests to crime-scene evidence.
VGL was created in 1999 to assist with the overwhelming number of cases that involve animal evidence. Today, the lab provides analysis, DNA testing and genetic testing on forensic evidence for the general public, as well as to federal, state and local law-enforcement agencies. Their findings have led to several prosecutions
One of the lab’s earliest cases was a sexual assault in Iowa where the victim was unable to positively identify her attacker from a police lineup. The woman remembered that her dog had urinated on the suspect’s pickup truck. The dog’s DNA matched DNA traces found on the pickup truck’s tire and the suspect confessed to the crime.
In another case, the VGL used DNA testing to match dog excrement found on the bottom of a murder suspect’s shoe to excrement found near the crime scene. This crucial bit of evidence helped secure the man’s conviction.
“When the lab first started, we were doing a lot of civil work — missing pets, insurance claims and identity testing, to confirm lab samples,” Wictum says. “Now it’s mostly criminal cases. I think that’s because more agencies are learning that we are here. We handle about a hundred cases each year, but the number of samples in a case can vary tremendously. We have a case right now with more than 400 samples.”
The VGL claims to have the largest database of domesticated-animal DNA in the United States. They test approximately 250,000 samples a year for parentage, coat color and disease diagnostics, which puts their database in the millions. The majority of those samples are from horses, but the lab also tests cattle, bison, yak, llamas and alpacas, sheep, goats, pigs, deer, elk, cats and dogs. “We are also fortunate to have access to sample collections belonging to our various research units,” Wictum says. “Samples are solicited for a variety of research projects, so if we need a reference database for a forensic case, we can quickly pull and test those samples.”
The testing performed on animal DNA is the same that’s done on human DNA. “We use the same tools and techniques, but our reagents are species-specific,” Wictum says. “If there’s a mixture of cat and dog or human and dog, we would only test the species we were interested in. Because we use the same tools as human forensic scientists, our evidence has been allowed into court without the scrutiny that the human testing labs faced in the beginning.”
When scientific evidence is used in court, there are standards (such as the Daubert and Frye standards, as well as the Federal Rules of Evidence) that it has to meet in order to be admitted. Human DNA testing was challenged repeatedly when it was first used in court, but it’s now generally accepted.
The VGL processes a variety of cases, including lost pets, animal abuse and animal attacks. Occasionally, DNA testing has exonerated animals suspected in an attack, and as a result, saved them from being euthanized.
“We’ve been doing a lot of animal-cruelty work lately,” Wictum says. “It’s emotionally difficult to work on cases where the victims are animals or children, but if we can get an answer, then we know we are helping to get justice for the victim. We’re also seeing an increase in cold-case homicides. Investigators reviewing unsolved cases often find pet hair associated with a case. Tests are now available that weren’t there 15, 20 or 30 years ago.”
Teaching forensic science
As the field of animal forensics grows, so does the need for training. Purdue University in West Lafayette, Ind., was the first veterinary school to offer students a course in forensic veterinary medicine.
“I realized there was an increasing amount of information out there, but nothing on the veterinary student level,” says Janice E. Sojka, V.M.D., M.S., Dipl. ACVIM, associate professor of large animal medicine at Purdue. Sojka became interested in animal cruelty and forensic medicine after starting PetSafe, a safe-haven program offered by Purdue’s School of Veterinary Medicine.
The objective of the course, which is an elective for sophomores and juniors, is to introduce students to the breadth of forensic medicine as it relates to animals. “We talk about such things as the law, pit-bull issues and dog fighting,” Sojka says.
According to Sojka, every small-animal practitioner encounters a handful of animals each year that are probable victims of cruelty or abuse. “Unfortunately, it’s something each student who becomes a veterinarian is probably going to see,” she says. “As individual they need to be prepared when that type of situation walks through their door. It behooves them to know how to approach the animal, and if the animal is a victim of abuse or neglect, they will know who to call and how to respond.”
Merck was involved in developing the nation’s first American Society for the Prevention of Cruelty to Animals Veterinary Forensic Sciences Program in conjunction with the University of Florida in Gainesville. The program will promote the application of forensic sciences to veterinary medicine to aid in the understanding, prevention and prosecution of animal cruelty. It will also be directly involved in forensic work on animal-cruelty cases investigated by the ASPCA and act as a resource to assist other agencies with such investigations. The class is slated to begin at the University of Florida in spring 2010.
The impact of animal DNA
“Right now, very few labs in the world are doing this work,” Wictum says. “If you think about how many homes have pets and how easily pet hair transfers, a tremendous amount of evidence isn’t being utilized. I think animal DNA testing will become much more common in the future.”
The problem right now, according to Wictum, is that most crime labs have their hands full testing human DNA evidence, and there isn’t funding to support animal forensic testing.
“People ask if there’s an increase in animal cruelty,” Merck says. “I don’t think there is, but I do believe there is an increase in responses, investigations and prosecutions. I also think in 10 to 15 years, we’ll start seeing special courts or special prosecutors and special judges.”
Merck also believes that it takes a special person to deal with animal-cruelty cases. “These are disturbing cases, so not everybody embraces them,” she says. “Putting animal cruelty cases on a court docket that also has rapes and homicides overloads the judges.” She suggests that more focused prosecution is needed because when courts try to equate animal-cruelty cases to other types of crime, it’s not the same.
Merck adds that veterinary forensics is growing. “More veterinarians are getting involved and more crime-scene investigators and law-enforcement officials are getting trained on animal cruelty,” she says. “Cases do better when we have forensics. The more forensics, the better the outcome.”
A case of mistaken identity
For one family that believed the wrong dog had been returned to them by their local boarding facility, forensic testing helped prove their case. After boarding their dog while on vacation, the family noticed changes in their Labrador Retriever’s behavior when they picked him up. They also believed the dog looked slightly different from what they remembered. When questioned, the kennel insisted that the correct dog had been safely returned to them.
The family sent some of the chew toys that belonged to the original dog, as well as a cheek swab from the suspected imposter, to the University of California Davis Veterinary Genetics Laboratory in Davis, Calif. The DNA on the toys failed to match the DNA of the dog currently living with the family, proving that the kennel returned the wrong dog. Although the original dog was never found, the family did receive a civil settlement based on the DNA evidence, and they kept the replacement dog as their pet.