Cats, Dogs, and DNA

22 Mar

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


6 responses to “Cats, Dogs, and DNA

  1. Dawn Kravagna

    March 22, 2010 at 9:04 pm

    Very interesting. I didn’t realize that cat hair could be traced to a particular animal. Thanks for the article.


  2. Sandra Parshall

    March 23, 2010 at 7:35 am

    Doug, does animal DNA indicate breed? Could the fact that an unknown dog is, say, a German Shepherd or a pit bull be determined from DNA in blood?


    • D.P. Lyle, MD

      March 23, 2010 at 11:48 am

      If they can get nuclear DNA from a hair follicle of the shed or yanked out fur, then yes the breed can often be determined. As you would suspect all breeds share a great deal of their DNA from just being canines, but some of the DNA can indicate the breed. And of course doggy family trees can be constructed just as human ones can—DPL


  3. Ann Littlewood

    March 24, 2010 at 12:06 pm

    Another fascinating post. Thanks so much for all the great information you make available. I can use this one for sure!


  4. DogBreed

    April 17, 2010 at 2:19 pm

    While doing a research for a project about dogs I found your blog. Thanks for the info


  5. shelly

    December 8, 2011 at 6:38 pm

    Just to clarify a few facts in your post– She was found several months after her disappearance. The jacket was not found with her body it was found long before her body in a different location and without the cat hair was of no use in the investigation.



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