November 18, 2008
Lab glitch hard to track
DNA unit chief skeptical on knowing the full problem
Testifying yesterday in a murder trial, Rana Santos, a supervisor in the Baltimore crime lab's DNA unit, gave the most complete picture yet of the Baltimore Police Department's review of DNA contamination but suggested that a full accounting of the problem could be difficult to produce.
Santos explained that on Aug. 8 she entered employees' DNA profiles into a statewide database and within hours learned that 12 previously "unknown" profiles in evidence processed by the lab actually belonged to lab employees. About 65 lab employees submitted DNA samples, and police spokesman Sterling Clifford said that eventually all 110 employees, as well as many former employees, will submit DNA profiles for the database.
But her testimony in the murder trial of Brandon Grimes shows that finding all of the samples tainted by lab employees could be laborious.
The state database - called CODIS - only accepts full DNA profiles. Partial and mixed profiles often are used in court, such as in the Grimes case, and those "thousands" of samples must be compared by hand to the profiles of lab employees, Santos said.
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"We'll need to go through every single one of our cases in the future," Santos testified, adding that there's no timeline for the review at this point.
The discovery of contamination also prompted procedural changes in the lab, Santos testified. Clifford said last week that no changes at the lab were necessary other than the addition of the employee DNA to the database.
Most of the "modifications to procedures," Santos said, are in the serology unit, a section of the lab that analyzes blood and other bodily fluids. That's where genetic material is collected before it moves on to the DNA unit. Serology employees will now wear two sets of latex gloves and use disposable rather than reusable gowns when handling evidence, Santos said.
Santos did not say whether procedures in other lab units had changed. Clifford said he was unaware of any other procedural changes. Police Commissioner Frederick H. Bealefeld III has asked the American Society of Crime Laboratory Directors/Laboratory Accreditation Board to review the lab. That board accredited the lab in December 2006.
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