A city crime lab employee left his own DNA on the pistol police say was used to kill an off-duty Baltimore detective, indicating that a recently discovered problem with contamination at the lab may be more widespread than officials originally believed.
Evidence from the murder trial of Brandon Grimes was not among the 12 instances city officials identified last week in which lab employees introduced their own DNA into crime evidence. But lab officials testified yesterday that there are thousands of partial strands of unknown DNA in evidence samples - like the one recovered from the pistol in the Grimes case - that must be checked by hand.
The Grimes case is the first in what city defense attorneys expect will be widespread challenges to DNA evidence processed in the Baltimore lab, whose director was fired last week amid concerns about contamination. In a scene that could play out in other trials, Grimes' attorney attempted to use the problems at the lab to broadly impeach physical evidence usually thought to be unassailable.
Rana Santos, technical chief of the lab's DNA section, said she checked the sample in the Grimes case Monday evening after reports of the contamination appeared in the media and she met with Grimes' defense attorney, Roland Walker.
Santos yesterday told jurors hearing Grimes' case that the original 12 cases of contamination, which she discovered Aug. 8, were "not surprising" to her "at all," given the growing sensitivity of DNA technology and the possibility that "simply breathing" could cause it. She also said that labs in other large cities have experienced similar problems.
To help the jury understand, Santos compared the lab to an operating room. No matter how pristine, "patients still come out with infections," Santos said.
Prosecutor Kevin Wiggins also repeatedly asked Santos to explain to the jury that forensic scientists can distinguish people's DNA from one another, even when they are found in the same sample.
"If two people's DNA are mixed, it doesn't equal someone else," Santos said.
But Walker criticized the state for not checking the evidence in Grimes' case as soon as news of the contamination broke, which coincided with the start of Grimes' trial.
"The only way I ever learned about this was from reading it in the newspaper," Walker said.
Grimes was in the middle of a "horribly serious murder trial," yet "nobody bothered to tell the defendant and his lawyer" about the contamination, Walker said.
