Rape-case attorney attacks DNA lab accuracy

Court rules require prosecutors to tell defense attorneys about evidence that could help prove a defendant's innocence.

Defense attorney Jacob Amaru contends that the failure of Deputy Pima County Attorney Michelle Araneta and the Tucson Police Department failure to own up to DNA contamination problems amounts to withholding evidence. And he says the DNA lab's problems could scuttle some cases.

Amaru represents Walter Ward, who is accused of raping a 14-year-old girl outside a Tucson convenience store.

When senior DNA analyst Nora Rankin was asked during a pretrial interview about instances of DNA contamination, she acknowledged one such incident, Amaru wrote in court documents.

But he and fellow defense attorney John Seamon learned of five other incidents involving Rankin from a fellow defense attorney.

In three of those cases, Rankin's DNA somehow got into the sample. In three others, she discovered contamination from some other source. They were among 24 known DNA-contamination incidents at the Tucson Police Department lab in the last seven years. None resulted in cases being dismissed.

Though there was no DNA contamination in the Ward case, the Pima County Attorney's Office should have revealed the incidents, Amaru wrote.

"At the very least, the reports from Ms. Rankin clearly illustrate a pattern of misconduct or incompetence in regard to the lab's ability to handle DNA without contaminating it," Amaru wrote in asking for the dismissal.

There are no industrywide standards for what an acceptable number of errors are, said Susan Shankles, the Tucson Police Department's crime lab superintendent.

But given the sensitivity of the testing done nowadays, the more cases analysts do the greater the chances of their DNA showing up, Shankles said. "It's a part of doing business."

The fact that the Tucson Police Department lab has written incident reports indicates that it has quality-control procedures established, said Vladimir Bolin, chief executive officer for Chromosomal Laboratories in Phoenix.

"It illustrates that they have a system in place and that it's working," Bolin said. "They are finding problems and taking steps to make sure they don't happen again."

But William Thompson, a professor of criminology at the University of California-Irvine, said problems with DNA testing are too often kept under wraps.

DNA contamination is typically "a family secret, like the uncle who drinks too much," he said, and because some labs aren't as open about their errors as others, jurors and members of the legal community tend to think DNA evidence is completely trustworthy.

There are plenty of chances for mistakes to be made in DNA labs if the proper protocols aren't in place, Thompson said.

David Berkman, Pima County's chief criminal deputy county attorney, said the contamination history isn't relevant, except to the specific case on which a mistake was made.

"What they're saying is there can never be contamination, but there's never been a lab where there's never been contamination," Berkman said. If an extraneous DNA profile shows up in a test result, the test is simply redone, he said.

"If a technician (made a mistake) on only four items out of 2,500 items tested, would that fall below the standard of care?" Berkman asked.

The lab workers at the Tucson Police Department are highly skilled people, Berkman said.

"I have a very high confidence level with TPD's crime lab," Berkman said. "They're all very credible people, and Ms. Rankin is an excellent technician."

Pima County Public Defender Bob Hooker said his attorneys understand that lab workers aren't infallible.

"The mistake is not that the lab made mistakes. The mistake is that the prosecutors tried to keep it a secret," Hooker said.

"I wonder how many cases the analyst testified in after these screw-ups and the prosecutors never disclosed it. I also wonder if there's a potential for appeals in those cases."

Chances are, Rankin isn't the only analyst whose DNA has ended up on pieces of evidence, Hooker said.

Shankles said the contamination in the 24 Tucson Police Department lab incidents came from a lot of sources, not all of which the department had control over. In some incidents it came from an analyst. In other incidents equipment, such as test tubes, had been contaminated where they were made, she said.

The six DNA analysts at the Tucson Police Department each handle about 114 cases a year. Last year they completed 684 tests, and there is typically a backlog of 200 cases, Shankles said.

Because DNA testing has become so advanced, DNA labs have a very stringent system of checks and balances in place to catch contamination, Shankles said.

Every report must be approved by two reviewers who make sure proper procedures were followed and the data and conclusions are correct.

"If there are any questions, the tests will be repeated. If we can't address the issues, the report will say the results were 'inconclusive,' " she said.

All analysts are required to wear coats, gloves and masks, and there are specific guidelines for cleanliness and keeping unknown and known DNA samples separate, Shankles said.

The Tucson Police Department's lab has been accredited by the American Society of Crime Laboratory Directors Laboratory Accreditation Board since 1993, Shankles said. The DNA lab is inspected every two years during a weeklong process.

Still, everyone familiar with the process acknowledges that mistakes happen.

Criminology professor Thompson recalled one instance in which a murder suspect's DNA was collected at his house and accidentally labeled as being DNA taken from a murder scene.

In an article written last year for the National Association of Criminal Defenders Lawyers, Thompson described how lab workers in Washington state accidentally contaminated evidence in a rape case with the DNA of an underage boy. The rape case was so old, there was no way the boy could have committed the crime.

Addressing the contention that mistakes don't count as mistakes if they are detected and corrected with retesting, Thompson wrote, "The same processes that can cause detectable errors in some cases can cause undetectable errors in others."

"Errors that incriminate a suspect are unlikely to be treated as errors; they are likely to be treated as incriminating evidence," Thompson wrote. "Consequently, the fat file full of errors should not be taken as evidence the system is working. They are a warning signal that we need to worry about errors the lab did not catch."

Whether the error history becomes an issue in the Ward case will be argued before Pima County Superior Court Judge Richard Fields on June 4.