In at least nine homicide, sex assault and burglary cases, Baltimore police detectives instructed crime lab technicians not to follow up on convicted criminals' DNA found on evidence at crime scenes because they determined it was not relevant to their investigations, police said.
Baltimore State's Attorney Patricia C. Jessamy has requested a complete review of cases handled by the lab, saying that prosecutors and defense attorneys need to be made aware of all the evidence police collect.
"We're working on it," Jessamy said Thursday. "We don't know the full extent of it."
Police spokesman Sterling Clifford played down the significance of the discovery, saying detectives routinely make judgment calls on evidence. But he said the department's policy has been changed and that officials are now hand-searching case files for similar irregularities, a process that is expected to take a "significant amount of time."
Last month, longtime city police crime lab director Edgar Koch was fired after the discovery that a dozen "unknown" genetic samples found in evidence actually turned out to be the DNA of lab employees. Defense attorneys and forensic experts said flaws that allowed such contamination to occur likely indicated more widespread problems at the lab.
But the revelation that police did not follow up in cases when DNA found on evidence collected at crime scenes was matched to the profiles of convicted criminals stored in the FBI's database is likely to stir greater alarm. It raises the possibility that other suspects or co-defendants might not have been pursued, or that charges were dropped in cases where the ignored DNA might have offered a smoking gun.
Police and prosecutors would not provide details about the nine cases, which include six open homicide and sex assault cases and three closed burglary cases over the past seven years.
Walter F. Rowe, chairman of the forensic science department at George Washington University, said he had never heard of such an issue and said it was standard procedure for police to follow up on DNA matches.
"It's something where you'd argue that prudent police work would involve ascertaining exactly where this guy [whose DNA was matched] was at, what his story is. Maybe he had been there at one time, or maybe he was an accomplice," Rowe said. "I don't think it can be cavalierly brushed under the rug. If the case isn't absolutely iron-clad, then you've got reasonable doubt."
At a crime scene, detectives mark items of possible evidentiary value, which are photographed and collected by technicians. Detectives may later decide that certain items are not relevant to the investigation, but they are tested for DNA nonetheless, Clifford said.
"Very often those crime scenes are enormous, sometimes covering entire city blocks," Clifford said. "You can imagine that a great deal of material gets picked up that's later determined to be too old or just not connected to the crime where it was picked up."
Because the items were deemed irrelevant, the presence of a criminals' DNA was not considered important, he said. Still, Col. John Bevilacqua, the head of the criminal investigations division, has ordered a change in policy since the issue arose.
"In a city where close to 100,000 people were arrested in one single year, the chances that you're going to turn up evidence of somebody with a criminal history being at or near a crime scene are pretty good," he said.
Jessamy said it was up to her office, not the Police Department, to determine whether the unreported hits are relevant to the cases.
"We make that decision," she said.
Such evidence must be offered to defendants and their attorneys during the discovery phase of their trials so that it is available to use in their defense. Prosecutors are examining the cases to determine "what, if anything" should be done, Jessamy said.
Defense attorney Donald Daneman said one of his recent cases might be among those in which DNA hits were not pursued. He said he was informed by prosecutors that DNA lifted from a beer can picked up two blocks from the scene of a shooting matched someone besides the defendant.
Though a jury found his client guilty of attempted first-degree murder on Sept. 10, Daneman said the beer can evidence would not have been a factor. He said he was more concerned about the broader problem of evidence disclosure.
"It wasn't a question of my client drinking a beer," Daneman said.
Michele M. Nethercott, who runs the public defender's Innocence Project in Maryland, expressed frustration that evidence-collection issues continue to emerge. She criticized Koch, the former lab director, and said his lack of "fastidiousness" combined with the high volume of cases caused the problem.
"This is coming out in dribs and drabs," Nethercott said. "First they tell us they fired the lab director, and it's no problem. Then they tell us the contamination is limited to crime scenes, then we find out it's in the lab. Now this."
On Thursday, the Detroit Police Department's firearms laboratory was shut down after a state police audit prompted by tainted firearms evidence called into question all forensic evidence handled in the lab over several years. Of 200 cases reviewed in the audit, 10 percent were found to have errors, a rate that experts called "10 times higher" than an average lab.
Clifford, the police spokesman, defended Baltimore's embattled lab, explaining that the decision not to pursue DNA database hits did not come from technicians.
Rowe, chairman of the nation's oldest forensic science department, said that given the scrutiny, detectives may be more likely to discard evidence that they determine to be irrelevant rather than have it tested. Detectives need to be careful not to create the perception of having a "confirmation bias," he said.
"You don't want people to think that you've made up your minds and don't want to get confused by facts," Rowe said.
Baltimore Sun reporter Melissa Harris contributed to this article.