Relying on a hit from the state DNA database, Baltimore police arrested a suspect last year in the long-unsolved rape and killing of Lisa Barselou, a 26-year-old who was assaulted and then submerged in the bathtub of her Bolton Hill home in 1989.
Kevin Gerald Robinson is scheduled to stand trial in October.
But the key to the case against Robinson, 42, is DNA, and recent testing revealed that part of the usually unassailable evidence was contaminated by a crime lab employee who left behind his own genetic material, a recurring problem at the Baltimore Police Department crime lab that led to the firing of its director this week.
Robinson's attorney said the lab employee's DNA could prove useful in discrediting the entire case.
"It goes to the lab's overall ability to control contamination," said attorney Nicholas Panteleakis. "If that's contaminated, what else is contaminated?"
Robinson's case is an example of the problems authorities could face as a result of DNA contamination at the lab. In a partial review, police found a dozen instances out of 2,500 where a previously unknown genetic profile turned out to be that of a lab employee.
A more thorough review is pending, said Margaret T. Burns, a spokeswoman for the Baltimore City state's attorney's office.
Police officials told senior prosecutors that once they have cataloged the DNA of all relevant lab employees, they will compare those profiles to about 6,000 "unknown" DNA samples, she said.
About 65 employee profiles have been developed, Burns said, and prosecutors are unsure how many more employees will submit samples and what the timeline for the review is. The crime lab has been testing DNA since 2001.
"The state's attorney is unclear so far as to the scope of the contamination and its effect on open and closed cases," Burns said.
Sterling Clifford, a police spokesman, confirmed that the staff profiles were still being gathered but said officials are confident the problem has been cornered. He said the employee contamination did not lead to any wrongful convictions.
An initial review by the lab, conducted last Friday, showed that employees had contaminated DNA samples in two court cases, Robinson's and a handgun violation case that ended with a guilty plea in December 2007, the law enforcement sources said.
The other DNA samples reviewed so far were not connected to cases that resulted in arrests, Clifford said.
