Problems handling DNA evidence at the Metropolitan Police Department's crime lab have not been limited to two cases in 2001 that garnered headlines this week.
In 2008, numerous mistakes by a lab technician slipped past lab supervisors and nearly made it into a death-penalty trial, according to court transcripts. The mistakes prompted an audit at the lab of 10 percent of cases over three years, according to the technician's testimony.
The case was the trial of Bryan Crawley, who was charged with killing Las Vegas businessman John Herda. There were several pieces of DNA evidence, although they were not critical to the case against Crawley.
The technician, who had been with the lab three years, testified that she made 10 mistakes in handling the evidence. Most were minor, such as writing the wrong location of a piece of evidence on a form. Other times she confused the type of samples she had and whether DNA was found on them.
The mistakes went unnoticed for two years, until the Clark County District Attorney's office alerted police to the mistakes just weeks before the case went to trial.
"We're taking this seriously and we're now going back and auditing 10 percent of the cases that have been done in the last three years to see if this is an issue in other cases," the technician testified.
Defense attorney Christopher Oram, who handled the case, said the mistakes were not critical to the trial; Crawley is serving a life sentence for the crime. But he said that case, along with revelations this week that DNA errors in 2001 sent the wrong man to prison for four years, could be used by defense attorneys to cast doubt on usually powerful DNA evidence.
"I think that's going to substantially hurt the power of DNA in Southern Nevada," he said.
Las Vegas police Assistant Sheriff Ray Flynn said he could not verify the technician's statements Friday night, but he emphasized the fact that the mistakes did not include misidentifying suspects in a case, which would have been more serious. He said the department believes that has happened only twice, in 2001.
"We're dealing with people's lives when this stuff comes up," Flynn said. "The most critical mistake we make is when we've misidentified somebody and we don't catch it."
The department on Thursday announced one of its lab technicians in 2001 swapped the DNA samples of two cousins, Howard Dupree Grissom and Dwayne Jackson, which eventually sent an innocent Jackson to prison for robbery for four years. They realized the mistake in October after California authorities matched the DNA of Grissom, who was in prison for attacking a woman, with DNA from the 2001 case mistaken to be Jackson's . The department is now reviewing more than 200 cases where that technician handled DNA evidence.
Attorneys on Friday did not minimize the impact of the error, which horrified police, prosecutors and defense attorneys alike.
"This makes all of us pause about what we're doing," said Clark Count Public Defender Phil Kohn. "We're professionals. This should really concern everybody."
His office is now launching a review of DNA evidence in active murder cases and other active cases where DNA was a central part of the prosecution's case.
"You're always going to have human error in the system," he said. "This makes us re look at everything we do."
Forensic DNA analysis is a relatively new type of evidence glamorized by crime shows such as "CSI: Crime Scene Investigation." It was introduced in the mid-1980s, and the Metropolitan Police Department's crime lab has been conducting its own analyses since 1997.
Attorneys said the mistake highlighted the ability of DNA to persuade juries and convict suspects.
"This is just one of those examples that shows although DNA is very powerful, when it's pointed the wrong way it is equally powerful and very difficult to clear up," said Michael Pescetta, an assistant federal public defender in Las Vegas.
JoNell Thomas, who handled criminal appeals for a dozen years, cautioned that DNA isn't foolproof.
"There can be problems," she said. "It's critical that defense attorneys get enough funding to do their own testing and challenge the state's evidence."
In cases where people have already been convicted of a crime, Kohn said it's difficult for defense attorneys to handle those appeals -- typically, the appeals complain of inadequate attorneys. He urged attorneys who handle appeals to look seriously at reviewing cases where clients were imprisoned solely on DNA evidence.
Pescetta said his office, which handles federal post-conviction appeals, already examines closely the handling of evidence at the police forensic laboratory because of the potential for human error.
"This is not a broad indictment of everything that Metro does, this is an area where mistakes can be made," he said.
Despite the mistakes, which police chalked up to "human errors" that automation now prevents, the Metropolitan Police Department has defended the forensic laboratory and the work of its staff. The lab is accredited as a member of the Combined DNA Index System, or CODIS, a federal database of DNA samples. It joined the system in 2000.
Because it is a member of the database and another accrediting organization, outside auditors examine the lab every five years, and DNA from an external audit team must be looked at every two years. Those auditors also look into five cases from each lab analyst in every section of the lab, with the ability to pull additional files, according to the department. The lab must also audit itself every year.
Kohn said he was surprised to learn that the technician who made the mistake in 2001 was lab veteran Terry Cook, with whom Kohn has worked before. Cook has been on paid leave since May.
"I know Terry Cook. He's not a bad guy, he's a good guy. He just made a horrible mistake," Kohn said.
Attorneys praised Las Vegas police for owning up to the mistake.
"I think it's great that Metro stood up here and admitted their mistake," Thomas said. "I think they should be commended."
Kohn said: "It gives me confidence in Metro that they don't bury their mistakes."
Contact reporter Lawrence Mower at firstname.lastname@example.org or 702-383-0440.