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Original Article

DNA reliability under fire
Evidence in Tucson, Florida cases contaminated by unknown source

Robert Anglen The Arizona Republic Dec. 12, 2005 12:00 AM

Evidence from criminal cases in Arizona and Florida, including a rape, a murder, and an assault, has been contaminated with the DNA of an unknown female who has no connection to either the suspects or the crimes.

The unknown DNA has been detected in at least three cases in Tucson and an undisclosed number of cases in Florida, leaving authorities pointing to possible contamination from a supplier of testing materials to crime labs.

Prosecutors and police say the presence of unknown DNA does not hinder their ability to prosecute suspects or negate other evidence in the affected cases.

But defense attorneys and legal experts say that the issue raises serious concerns about the reliability of DNA evidence and they say the potential impact of the contamination is dramatic and disturbing.

The spread of the unknown DNA might not be limited to the two states, since police labs nationwide tend to use the same small group of suppliers for items such as Petri dishes, test tubes, measurement devices, filters and reagents.

"It is a profile we can't attribute to someone in a case or someone in a lab," said Susan Livingston, forensic services director for the Florida Department of Law Enforcement in Tallahassee. "We have not been able to pinpoint the source of the contamination. . . . It is something we may never figure out. But it certainly raises the question of what our two states have in common."

DNA: The holy grail?

"DNA is considered the gold standard of forensic science. It is the holy grail of evidence. What happens when we find out that the holy grail is contaminated?" Phoenix lawyer Larry Hammond said. "The whole CSI phenomenon is going to be called into question."

Hammond is founder of the Arizona Justice Project, which has used DNA to exonerate a death row inmate and a convicted child molester and has helped create a national institute on forensic science in criminal cases.

"I want there to be things you can count on in the criminal justice system to convict the guilty and acquit the innocent," Hammond said. "You don't have that if the top, most scientific tool you have is contaminated."

Hammond said the cases in Florida and Tucson need to be reviewed by an impartial panel to determine if the cases have been jeopardized. And he said it is imperative to identify the source of the contamination.

"This is very disturbing," he said. "It calls into question all of the related cases."

DNA refers to deoxyribonucleic acid, the genetic material found in the cells of almost all living things. DNA is considered the biological equivalent of a fingerprint, in that every person has a different DNA structure.

Criminalists in forensic laboratories have used DNA to identify or rule out suspects in crimes by matching their DNA to samples of DNA in hair, tissue, semen, blood and saliva found at crime scenes.

The Tucson cases

Records from Pima County Superior Court show that the unknown DNA was found in three cases handled by the Tucson Police Department crime lab.

On Nov. 17, a Tucson criminalist reported that the unknown female DNA was found on earrings stolen from a woman during an assault. However, the DNA did not match anyone associated with the case, including the victim or the man charged in the crime.

The same unknown female DNA was found on a cigarette butt that was evidence in an unrelated Tucson homicide case.

It was also found on a gun used in an unrelated Tucson assault case. The gun was seized from a vehicle driven by a man who was traveling with two other men. No females were in the vehicle at the time.

After discovering the unknown DNA, the Tucson crime lab contacted the Florida Department of Law Enforcement, which maintains a national database of unknown DNA profiles.

The database confirmed that the same DNA had been found in police laboratories in Florida, although officials there are not saying how many cases or law enforcement agencies are involved.

Crime lab officials in Tallahassee and Tucson are working together to find the source.

Susan Shankles, superintendent of the Tucson Police Department crime lab, said the unknown DNA likely entered the lab through equipment bought from a vendor.

"Certainly, I am concerned," she said. "But I think the lab has investigated and we can explain where we think it came from."

Shankles explained that much of the equipment used in the lab is guaranteed to be DNA-free. And since the discovery of the contamination, the lab has bought a $1,500 device that will eliminate DNA from everything else.

"Since this is the first time we've seen this type of problem, we're taking steps to make sure we don't see it again," she said.

Shankles acknowledged that crime labs in other states could be affected with the unknown DNA. But she said it is likely that the contamination is limited to a batch of equipment and could stem from something as simple as an employee sneezing in a manufacturing facility.

"It's not like it is swirling in the air," Shankles said. "Only those people who purchased this particular lot would be affected."

The unknown DNA has already affected one of the Tucson cases.

Prosecutors in the sexual assault case argued in a Pima County court last week that the unknown DNA found on the victim's earrings is not relevant and doesn't affect other evidence against the suspect, Daniel Lopez.

In a pretrial motion, prosecutors said jurors shouldn't even be told of the unknown DNA. "It is irrelevant to any issue or evidence being introduced," Deputy County Attorney Shawn Jensvold said.

At the same time, he said, if "the mere mention of the earrings opens the door for the defendant to probe into the DNA testing of the earrings, then the state will avoid any mention of the earrings."

Since the earrings were allegedly stolen at the time of the assault, not mentioning them would eliminate a piece of evidence linking the suspect to the crime.

A lawyer with the Pima County Legal Defender's Office, which represents Lopez, said the unknown DNA calls into question all of the DNA evidence against Lopez. The attorney says the jury needs to know evidence in the case is contaminated.

Shankles said the crime lab doesn't support any outcome in any case.

And DNA is used to eliminate a suspect from a crime as often as it used to implicate someone.

"We analyze evidence for whatever it is," she said. "We have no vested interest in going one way or another. . . . We analyze the evidence to the best of our ability."