Solving Human Crimes with Animal DNA
Written by Beth Wictum & Trina Wood   

Her body was found nude in a wooded area of Florida, wrapped in a bed sheet and shower curtain that was secured at the head and feet with duct tape. Shantay Leann Huntington’s cause of death: asphyxiation. Male DNA was recovered from the duct tape and shower curtain, but the profile didn’t match known samples in CODIS. After her male traveling companion was eliminated as a suspect, the case went cold.

Three years later, the Veterinary Genetics Laboratory Forensic Unit (VGL Forensics) at the University of California, Davis received 13 dog hairs from the bed sheet for DNA analysis. Two of the hairs contained enough DNA to profile. Although they weren’t an exact match to the two dogs who lived across the street from where Huntington was found, there was enough similarity to suggest that the hairs came from a full sibling of those dogs. Upon further investigation, it was discovered that two pups from that litter had been given to the homeowner’s brother-in-law, Guillermo Romero, whose wife had a restraining order against him by the time of testing. Law enforcement obtained samples of Romero’s DNA and matched it to DNA found on the shower curtain and duct tape used to wrap the young woman’s body. In 2013, Romero pled guilty to manslaughter.

How-to video: Buccal swab collection on a dog
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Animal DNA profiling is becoming more commonplace as investigators realize that the same techniques used in human DNA analysis can also be applied to animal evidence such as saliva, urine, feces, blood, and hair. Animal evidence can help solve a wide range of cases from animal cruelty or theft, to animal attacks on humans, and human-on-human crimes like robbery, rape, and murder. Dog feces evidence from two different violent crimes was analyzed and presented in court to help convict defendants in a triple homicide and in a rape. Dog urine from territorial marking on a truck tire was profiled in a sexual assault case, leading to a plea deal. Blood evidence found on the clothing of burglary suspects who silenced barking dogs by slitting their throats or by placing them in a lit oven was used successfully by prosecutors.

The scope of each investigation is only limited by the imagination of the investigator. As one of the first people to arrive, crime scene investigators have a unique opportunity to survey the crime scene and identify potential evidence. It’s the investigator who thinks outside the box and wonders, “What can this animal evidence tell us?” who comes to our door.


An alternate light source is used to look for biological evidence. Photo: Don Preisler

VGL Forensics is a public-service unit of the UC Davis School of Veterinary Medicine. Our DNA testing services are used by federal, state, and local law enforcement agencies as well as the general public. The majority of our cases are from the U.S. and Canada with occasional cases arriving from Great Britain, South America, Australia, and Japan as investigators reach out for assistance on hard-to-solve cases. As a part of one of the largest animal DNA testing laboratories in the world, we have databases available for dogs, cats, horses, cattle, sheep, goats, pigs, deer, elk, wolves, coyotes, bear, llamas, and alpacas—providing for a diverse range of potential cases. Despite there being more cats than dogs as pets, dogs are more likely to be involved in a case, with more than half of all our cases focusing on dogs. VGL Forensics handles approximately 100 cases a year, with cases involving up to dozens of samples. The cost of a case depends on the number of samples being tested, but averages about $2,000 and takes two to four weeks to test. In 2010, we became the first ASCLD/LAB-International accredited crime laboratory dedicated to animal DNA profiling.

DNA Testing and Pets


A buccal swab is used to collect a DNA sample from a cat.

Pet ownership in the U.S. has more than tripled since the 1970s. More than 60% of American households now include at least one pet, and those pets can help solve crimes. If you own a cat or dog, you know that their hair is accompanies you throughout the day; from your home to your car; from your car to your office. Pet hair is the most commonly collected item of non-human biological evidence. However—unlike humans—dog and cat hairs without roots can yield enough DNA for individual (nuclear) DNA profiling. That’s because when they groom themselves, they are leaving saliva on the hair shafts—and that saliva contains cells. About 1 in 15 shed dog hairs will have enough nuclear DNA for individual profiling. The more fastidious cats average about 1 in 4 hairs with enough nuclear DNA.

The likelihood of getting that DNA profile goes down when those hairs have been laundered, buried, immersed, or have had prolonged exposure to the outdoor environment. Even in those cases, another type of DNA (mitochondrial) found in all animals can be tested to include or exclude a suspect. Mitochondrial DNA has many more copies in each cell and is more stable due to its circular shape. Because it persists longer than nuclear DNA, it is especially useful when samples are degraded. It is inherited through the maternal line, so everyone—people and animals—has the same mitochondrial DNA as their mother. Even though it is not unique to an individual, it can identify or exclude possible contributors and assist in the progress of the investigation.

A single cat hair found in the out-turned pocket of a homicide victim helped to implicate his killer. Stephen Nolte was found with severe neck lacerations to the point of near decapitation. Upon investigation, it was found that he had engaged in a dispute with a former employee over money. His pockets were turned inside-out, and $450 dollars were missing, along with his truck. When the cat hair from his pocket was tested, it failed to yield an individual nuclear DNA profile, so mitochondrial DNA testing was done. The mitochondrial DNA sequence obtained from the cat hair had never been seen before in any of the cat databases. Cats from the suspect’s home and from the surrounding community were collected for comparison. While no matches were found in the area cats, 8 out of the 11 cats at the suspect’s house had the same mitochondrial DNA type as the evidence hair. A hearing determined that the cat evidence was generally accepted as reliable, and Henry Lee Polk was found guilty of first degree murder.


Saliva is swabbed from the sweatshirt of the victim in a dog attack. Photo: Don Preisler

Besides being the “witness” at a crime scene, animals themselves are frequently the victims of crimes. In addition to the crimes of dogfighting and animal cruelty, many serial killers have admitted that they began their careers with animals. However, animals are also often tortured or killed by someone trying to control another person in domestic violence situations. Up to 80% of women arriving at domestic violence centers report animal abuse by their partners. In the case of Jeffrey Nally Jr., his girlfriend’s mother reported that her daughter was being held against her will and that Nally had threatened to kill her if she tried to leave. A search of his home revealed 29 dog carcasses and three live puppies. On the day he was arrested, Nally had forced his girlfriend to hold a puppy while he drilled into its head. Hair recovered from the drill was matched to the dead puppy. Nally pled guilty to a lesser charge of nine counts of animal cruelty and weapons possession. While some jurisdictions still consider animal cruelty a misdemeanor, it has been well documented that it is a significant indicator for violent criminal behavior and states are starting to address that with broader statutes and increased penalties.

Animal DNA analysis can also be used to exonerate a suspect. In 1982, Wendy Lou Stark was abducted from a shopping center. Five hours later she tried to escape and was shot four times by her abductor. Witnesses saw a man bend over her body and remove a black and white puppy. A suspect was identified who shared a home with a family whose dog matched the description. Although hairs from her pants were visually similar to the dog, no further identification could be done at that time. Those hairs were analyzed by VGL Forensics when the case was reopened 27 years later. The DNA profile from the dog hair on her pants eliminated the suspect dog. The ability to eliminate suspects early in an investigation allows investigators to focus their efforts in other directions. Subsequent human DNA analysis of a vaginal swab got a CODIS hit to a man who had died in prison the previous year and had no obvious connection to the crime.

Collecting Animal Evidence

Even if you don’t plan to test animal DNA immediately, collecting the evidence and storing it correctly allows for later testing that could make or break a case. Since DNA is the same in each cell nucleus of an animal, buccal swabs are the preferred sample type for known cats and dogs. Buccal collection kits for live animals are provided by the laboratory at no cost. If you are collecting hair from a live animal, you should select the thickest hair and pull 10-20 hairs with intact roots. Hairs should be stored long-term in sealed paper envelopes. It is important that you sample all pets associated with both the victim and suspect for possible elimination later.

  • Transferred animal hairs are frequently found on clothing, vehicles, bodies, weapons, and bedding.
    • Do not permanently mount evidentiary hairs onto slides. If a visual comparison needs to be made, place a cover slip over the hair and tape the cover slip to the slide to preserve any cells on the hair shafts.
  • Animal DNA present on a person (for example, saliva from a bite or vaginal cells from a sexual assault on an animal) should be swabbed.
    • Collect these samples as soon as possible (less than 24 hours). Look for towels or pads that may have been used to wipe the skin.
  • Blood or urine on a large object should be swabbed. Allow smaller items to dry and submit the entire item.
    • When sampling from a suspected dog-fighting pit, select discrete blood spots or blood smears towards the top of the pit wall to minimize contamination from multiple dogs.
  • Feces evidence is usually present on shoes or clothing. Those items should be allowed to dry at room temperature and stored long-term in sealed paper bags.
    • Freeze wet feces immediately in a leak-proof container. If that is impractical, then allow it to air dry away from direct sunlight. Drying the feces is critical to prevent mold growth.
  • Food dishes, toys, brushes, crates, and bedding are good DNA sources when trying to place an animal at a home.
    • Submit the entire item or, if that’s not practical, swab the item. Identify how many animals have used those items prior to collection to minimize mixtures.

Animal DNA has been used many times and in many states. Sometimes it is the primary piece of evidence that drives the investigation. Sometimes it plays a supporting role, laying the groundwork or reinforcing other important evidence. Other times it can provide information that takes a case in another direction—even when that case has been cold for years. Much attention has been given to the “CSI effect”, and juries have come to expect forensic science in the courtroom. Since many of them are pet owners, they are fascinated by the animal DNA evidence and they become engaged when we testify about our work. It may not be the key to solving every case, but almost every case will have some animal DNA. Yours may be next.

For more information about VGL Forensics, visit: www.vgl.ucdavis.edu/forensics

About the Author

This e-mail address is being protected from spam bots, you need JavaScript enabled to view it began her career in animal testing in 1979 and switched entirely to forensics in 2000. She is the director of the forensics unit of the Veterinary Genetics Laboratory in UC Davis’ School of Veterinary Medicine.

 
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