Daily Archives: March 22, 2010

Cats, Dogs, and DNA

Some criminal cases are simply cool and this is one of them. Chrisdian Johnson’s dog told on him. Not in a Lassie-goes-and-tells-mom-you’re-in-trouble kind of way but more a Gotcha way.

On March 19th in London, Johnson was sentenced to 24 years in jail for the murder of 16-year-old Seyi Ogunyemi. It seems that Johnson used his pit bull, who he named Tyson, in an attack on Seyi. Once the dog brought Seyi down, Johnson stabbed the young man six times killing him. Johnson, now covered with blood, was arrested as he fled the scene. The blood turned out to be that of Tyson rather than Johnson’s or, more importantly, that of the victim. Apparently the dog had received injuries during the attack. DNA analysis showed that the blood on Johnson’s clothes and the blood found at the scene belonged to Tyson, which put Johnson at the scene of the crime even though he had not left his own DNA there. Sometimes things just work out.

This case reminds me of the famous Snowball the Cat case. In 1994, Shirley Duguay of Prince Edward Island disappeared. A few days later her corpse, along with a blood-soaked leather jacket, was discovered in a shallow grave. The blood turned out to be Duguay’s, but investigators noticed that the jacket also carried white cat hairs. Her estranged husband, Douglas Beamish, owned a white cat named Snowball. Blood taken from Snowball generated a DNA profile that matched that of the cat hairs found on the jacket, placing Beamish at the burial site. The DNA conclusively showed that those hairs didn’t just come from just any white cat, but rather from Snowball. Beamish was convicted in this landmark case, the first that utilized animal DNA to gain a conviction.

University of California, Davis scientists are currently collecting a database of cat hair Mitochondrial DNA so we might see more of this interesting technique in the future.


Posted by on March 22, 2010 in DNA, Interesting Cases

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