Plant’s DNA ‘Fingerprints’ Lead to Man’s Murder Conviction
PHOENIX (AP) _ They were only two tiny seed pods, but their DNA helped convict a man of murder in what prosecutors say was the first use of plant genetics in a criminal trial.
The two seed pods found in the bed of Mark Allen Bogan’s truck were matched by a University of Arizona plant geneticist to a palo verde tree at the site where Denise Johnson’s strangled body was found last May. On Wednesday, a Superior Court jury convicted Bogan, 34, of murder.
″The pods placed his truck at the scene,″ said William Clayton, the deputy county attorney who prosecuted Bogan. ″In getting this case to trial, I would say it was the key piece of evidence. Without it, the case would have ended up being dismissed prior to trial.″
Bogan, who is to be sentenced June 22, faces life in prison without possibility of parole for at least 25 years.
He became a suspect in the May 3, 1992 slaying after authorities found his telephone pager with Johnson’s partially clothed body in a remote area west of Phoenix. She had been strangled.
Bogan testified that he picked up Johnson, who authorities said was a prostitute, and had sex with her in his truck. But he denied killing the woman, and said she stole his pager.
Geneticist Tim Helentjaris testified that DNA patterns for the palo verde tree matched those of the seed pods. Prosecutors also said the tree’s trunk contained a scar consistent with being hit by Bogan’s truck.
DNA, or deoxyribonucleic acid, carries the genetic blueprint for all living organisms.
DNA analyses of human blood and semen have been admitted as evidence in hundreds of rape and murder cases since 1986, but Clayton said this was the first involving genetic testing of botanical life.
″The technique has been used a lot for human DNA, but not much for plant DNA,″ Helentjaris said Friday in a telephone interview from his university lab in Tucson. ″Maybe they’ll be more widespread application now.″
Helentjaris testified that DNA patterns for palo verde trees are at least 15 times more complex than those for humans, meaning his genetic match of the seed pods was far more conclusive than matching a person’s bodily fluids would have been.
Helentjaris told jurors he not only matched the two seeds pods to the tree at the crime scene but that the correct tree was chosen out of a ″lineup″ that included 11 others at the site and genetic samples from 18 more throughout Maricopa County.
Helentjaris, an associate professor of plant science, said he spent at least 100 hours analyzing the palo verde DNA, spending about $1,000 of his own money.
″It took a lot of my time, but I did it as public service,″ he said.