Forensic evidence - DNA on a victim, gunshot residue on a hand, fingerprints on a weapon - holds a special place in courtrooms, often treated as irrefutable proof that police have nabbed the bad guy. But the labs processing that prized evidence can sometimes become the suspects.
Last month, the Baltimore Police Department disclosed that its lab employees were leaving their own DNA on crime scene evidence. Lab director Edgar Koch lost his job because of the contamination, which had gone unidentified for years because the lab didn't take the basic step of cataloging employee DNA in a database.
The city's top prosecutor and police commissioner say the crime lab produces quality work that stands up in court.
"The vast majority of our lab employees are incredibly smart and talented people, scientists by trade," Police Commissioner Frederick H. Bealefeld III said, pointing to an employee who developed a date rape drug test used nationally. "They have done a lot to advance our lab."
But in recent years, defense attorneys have uncovered problems with the way crime labs across Maryland handle forensic evidence, and they've questioned the credentials of some prominent analysts. Last year, a Maryland State Police ballistics expert killed himself when it became known that he'd lied about his schooling. And years before the DNA scandal, the Baltimore lab admitted that its gunshot residue evidence could be tainted, in part because police firing ranges were too close to the lab area.
Even before the recent revelations about DNA processing in Baltimore, state legislators were so concerned about crime lab standards that they gave the Department of Health and Mental Hygiene oversight, beginning in 2011.
"Labs make mistakes. Scientists make mistakes. Published research can be wrong," said Walter Rowe, chairman of the nation's oldest forensic science department, at George Washington University.
"Most people's attitude toward science is that they're apt to accept its findings as gospel. There are some areas where the science is rock solid and incontrovertible. But there are other areas where we just think we know what's going on."
Each time a problem comes to light, defense attorneys warn that hundreds of cases could be jeopardized. But sweeping reviews, such as one undertaken in Houston five years ago when an audit revealed possible DNA contamination, often prove too costly and laborious, local defense attorneys say.
Because forensic science is a relatively new aspect of crime-fighting, with rapidly changing standards, it can be difficult to assess the quality of a crime lab. There are few watchdogs, said Patrick Kent, forensics division chief of the state public defender's office.
The American Society of Crime Laboratory Directors/Laboratory Accreditation Board accredits many labs across the country, including 13 in Maryland.
It is considered the gold standard of lab quality - something that lab employees almost always mention when they testify.
But the board is funded by the labs it accredits and rarely rejects an applicant or disciplines a member.
Kent said that becoming accredited "is akin to getting a mail-order diploma. If you have the money, they have the accreditation."
Labs pay an initial fee of $500 to $2,000 and annual fees of $500 to $40,000, depending upon the size of the lab, for accreditation. Ralph Keaton, one of the board's founders and its director, doesn't see a problem with the arrangement.
His board has accredited 343 labs. In its 25-year history, two labs did not complete the accreditation process (one has since restarted). To gain accreditation, Keaton said, labs must submit a self-audit, pay accrediting fees and allow inspectors into the lab to review work. After accreditation, labs must turn in annual self-audits and document technicians' continuing training and proficiency testing in fast-changing practices such as DNA testing.
Baltimore's crime lab was most recently accredited in December 2006.
In April 2007, Gov. Martin O'Malley signed a law giving crime lab oversight to the health department, which also oversees hospital labs. But the law has yet to be funded, and the governor has yet to appoint a committee to advise the department on setting lab standards. An O'Malley spokeswoman said he is reviewing applicants and will have the committee in place by the end of the year, as required by the law.
Sen. Delores G. Kelley, a Baltimore County Democrat who wrote the bill, said DNA contamination in the city crime lab "should be a clarion call" to move forward quickly. She added that crime labs could be inundated with DNA tests once a law goes into effect in January significantly expanding the pool of people whose DNA is collected and analyzed.