Genetic technique will help rape cases, UA researcher says

Dan Hoffman Arizona Daily Wildcat Research associate Hwa-Yong Park points at a portion of a Y-chromosome DNA profile in his lab last Wednesday afternoon while UA biological sciences researcher Al Agellon (left), and biotechnology researcher Mike Hammer (right) look over his shoulder. Park was recently hired to investigate possible forensic applications of Hammer's Y-chromosome research.

DNA analysis of male chromosomes is making the leap from pure science to criminology - thanks to UA research.

For 10 years UA biotechnology researcher Michael Hammer has been on the evolutionary trail of the male Y-chromosome. The chromosome remains virtually unchanged as it is passed from father to son.

In fact, Hammer has tracked the Y-chromosome of all men alive today back to a common ancestor in Africa and has followed migration patterns out of Africa to Europe, the Middle East and Asia.

But now, Hammer has turned to fighting crime.

In September, Hammer received a two-year, $140,000 grant from the National Institute of Justice to develop methods using Y-chromosome analysis in forensics.

"It makes sense to target the Y-chromosome because males have such a propensity to commit crime," Hammer said.

The grant funds research to develop standard techniques criminologists can use to help identify or exclude suspects in criminal cases.

"To develop Y-chromosome as a forensic tool, we're doing the same things we do to study evolution," Hammer said, "by looking at variations in Y-chromosome that would be useful to identify male perpetrators of crime," Hammer said.

The technique will be extremely helpful in rape cases, Hammer said.

DNA evidence plays a key role in many rape cases, and on occasion is the only evidence prosecutors can use to get a conviction, said Alan Hatch, a Tucson Police Department criminologist who will work with Hammer to verify and test Y analysis procedures.

But isolating a rapist's DNA from that of the female victim is a time-consuming procedure, Hatch said.

A crime lab must first isolate sperm cells.

"It's not hard to isolate them out if you have a large number of spermatozoa, but in most cases in the real world a victim has waited 12, 14, 18 hours before reporting it (a rape) and sat in an exam room for another three because a double shooting came in, so we are dealing with evidence that is severely compromised," Hatch said.

"If you can go in and look at the Y-chromosome, you can get a profile," he said.

Al Agellon, a UA biological sciences researcher who is working with Hammer on the Y-chromosome project, said the ability to get a DNA profile from the Y chromosome would save criminologists time.

"Because the Y is male-specific, it doesn't matter if the cells are all mixed up," he said.

"You don't have to go through all the procedures to isolate sperm and extract the DNA from the sperm. Crime labs can simply do a Y-specific test to get a profile of the male," Agellon said.

In cases where a rapist is sterile or has had a vasectomy, Y-chromosome analysis would be the only possible way to get a DNA profile, Hammer said.

"A vasectomized male still leaves aspermic semen that includes epithelial cells," Hatch said.

Epithelial cells are produced by the body anywhere a mucus membrane exists.

But there is absolutely no way to separate male from female epithelial cells, Hatch said, so without a Y-specific DNA test, it is impossible to get a genetic profile of a vasectomized or sterile rapist from semen, he said.

Both Agellon and Hatch said the Y test may be most important in excluding suspects from criminal investigations.

"You can do an exclusion right away and say ' this is not the guy.' This would save the crime lab a tremendous amount of time," Agellon said.

Hatch said the exclusionary power of DNA tests is usually underestimated.

"I probably clear more people than I convict (with DNA testing)," Hatch said.

"It's a very powerful technique for keeping people who were not the semen donors in crimes out of prison."

Hammer and Agellon are just beginning their work, and will collaborate with crime labs in Arizona, California and New York to verify and test their procedures.

"If things work out, we'd like to have something we can use within a couple of years," Agellon said.