Advanced DNA tests can offer new leads

Judi Villa

Arizona is the first of only four states in the country to begin advanced mitochondrial DNA testing that could help police solve some of their most difficult cases and even put names to unidentified remains.

Mitochondrial DNA (mtDNA) is inherited from the mother and can be an important tool in solving crimes or exonerating suspects, especially in cases with scant physical evidence. The testing is more specialized than the traditional analysis of nuclear DNA, the unique genetic fingerprint carried in each person's cells. Some samples, such as hair shafts, only contain mtDNA. In bones and teeth, mtDNA often can be extracted after the nuclear DNA has degraded.

"There are certain kinds of samples where traditional DNA does not work," said Todd Griffith, who oversees four crime labs for the state Department of Public Safety.

With mtDNA, Griffith said, "if you have a hair that's been shed that's associated with a sexual assault, and that's all you've got, that could be a very powerful piece of information."

The analysis isn't a unique identification like nuclear DNA, but it can identify an ancestral line since a mother, her siblings, her children and her daughter's children will have identical mtDNA.

Testing in Arizona began about a month ago at the state DPS lab in Phoenix. The FBI provides funding for the lab, the only one of its kind in the Western United States.

Griffith said the lab expects to process about 150 mtDNA cases annually, with many of those involving hair plucked from crime scenes. About 25 percent of the cases will be from Arizona. The rest, coordinated by the FBI, will be submitted by law-enforcement agencies across the country.

The testing has been done in the FBI's lab in Quantico, Va., since 1996 but has not been available in state crime laboratories because it is expensive and time-consuming. It takes six to eight weeks to complete an analysis of mtDNA, compared with about two to three weeks for nuclear DNA, Griffith said.

"This would be really exciting to get that mitochondrial DNA testing here," said Phoenix police Detective Bob Brunansky, who investigates unsolved murders. "That's a really, really good way of identifying a suspect."

"Let's say you don't have any semen or you don't get any DNA particles off a body. Let's say in a rape case or a case involving extreme violence, they leave a hair follicle. That's where the mtDNA becomes very important."

The DNA also can be used to compare DNA from a maternal relative to unidentified remains. Nearly 6,000 unidentified dead are listed in the National Crime Information Center database. In Maricopa County, nearly 200 bodies since 1973 have never been identified.

Griffith said that initial analysis will be aimed primarily at criminal cases, but the hope in coming years is to expand a national mtDNA database of unidentified remains.

"We are very excited," Griffith said. "It'll create some great additional capabilities."

Other mtDNA labs are located in Connecticut, Minnesota and New Jersey.