In 1994, Royal Canadian Mounted Police (RCMP) found a woman's body in a shallow grave in Prince Edward Island, Canada. She was identified as a 32-year-old woman named Shirley Duguay. The mother of five children, Duguay was separated from her common-law husband Douglas Beamish. Beamish had a criminal record and was on parole during the time of the murder. The primary suspect in the case was Beamish, however RCMP had no evidence to associate him with the crime.
Near the scene of the crime, RCMP found a leather jacket that was stained with blood that matched that of Duguay. Some of Beamish's friends told RCMP that they thought that Beamish owned such a coat, but they could not be certain. Forensic investigators studying the jacket found 27 white hairs on the inside lining. They initially thought that the hairs might belong to Beamish, but microscopic analysis showed that they were actually cat fur.
One of the investigators on the case remembered seeing a white cat named Snowball at the house of Beamish's parents. At the time of the murder Beamish was living with his parents. Proving that the white fur belonged to Snowball would provide evidence tying Beamish to the crime. While forensics investigators could tell that the hair belonged to a cat, their microscopic hair analysis was not accurate enough to assign ownership to a specific cat. Determining the identity of the individual animal that shed the hairs required genetic testing. However, the forensics investigators on the case had no precedent for DNA fingerprinting of cats.
An RCMP investigator contacted the Animal Genetics Group at the Laboratory of Genomic Diversity (LGD) in Frederick, Maryland. They agreed to attempt DNA fingerprinting of Snowball. RCMP took a sample of blood from Snowball and one of the hairs found on the jacket contained a root with enough DNA to perform an analysis. The primary geneticist in the case, Marilyn Menotti-Raymond, developed a method that looked for short tandem repeats (STR) in the cat's DNA. Both the DNA from the hair root and the DNA from Snowball's blood sample matched.
Investigators were concerned that because it is an island, Prince Edward Island is relatively geographically isolated. Therefore many of the cats on the island might be close relatives. If this were the case, the match between Snowball's blood sample and the hairs found on the jacket would be insignificant. To test whether this was a problem, RCMP collected cats from all parts of the island, including the area around the crime scene. They took blood samples from these cats and performed the STR analysis that Menotti-Raymond developed. The cats on the island showed a high degree of genetic variation, indicating that the STR match between Snowball and the hairs found on the jacket was significant.
Based on the genetic evidence linking Beamish to the jacket, he was convicted of second-degree murder and sentenced to prison for 15 years. The case set a legal precedent allowing DNA fingerprinting of animals to be admitted as evidence in criminal trials.
SEE ALSO DNA banks for endangered animals; DNA fingerprint; Hair analysis; PCR (polymerase chain reaction); Wildlife forensics.
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