Because people who work in labs have to handle the actual samples, so there's a slight chance of contamination by the technician's DNA. I don't know for sure, but it would make sense for lab workers who handle the actual physical samples to have their DNA profiles on hand at the lab for exclusionary purposes. These profiles of course would not go into a governmental database but would be kept on site as a working tool and most likely be deleted from their in-house system when that technician leaves employment. My recollection of Meehan's testimony was that there was a match from one sample to his DNA in the form of one skin cell but I don't remember him testifying that they took a sample from him at the time to test, so it seemed as though his profile was already available there to them. Yes, I'm certain he wore gloves. The comparison would have been for exclusionary purposes and his cell would not have presented as the actual sample under review. At any rate, a DNA lab technician's DNA on file at a lab would not go into any outside database.
You can probably find a fuller answer to your question by researching DNA lab procedures for technicians who handle samples.
Nifong Attorneys: DA Didn't Intentionally Violate Ethics Rules
Durham — Attorneys for Durham County District Attorney Mike Nifong tell the State Bar he did not intentionally violate ethics rules when prosecuting the Duke lacrosse case.
Nifong on Wednesday filed a written response to ethics complaints levied against him by the North Carolina State Bar in connection with the Duke lacrosse sexual assault case.
The embattled prosecutor had no comment Wednesday afternoon and referred all questions to his lawyers.
Attorneys for Nifong also tell WRAL they will file a motion to dismiss some charges that Nifong withheld exculpatory evidence from defense attorneys representing the charged Duke lacrosse players.
Earlier this year, the State Bar amended an earlier ethics complaint against Nifong alleging he withheld DNA evidence and misrepresented the truth to the judge in the case.
The original complaint, filed in December, accuses Nifong of violating professional conduct rules by making misleading and inflammatory comments about the athletes under suspicion.
The case stems from a March 2006 incident in which a woman claims she was sexually assaulted at an off-campus party, where she was hired to perform as an exotic dancer, by three members of the Duke lacrosse team.
A grand jury later indicted lacrosse players Collin Finnerty, 20, Reade Seligmann, 20, and David Evans, 23, on charges of first-degree kidnapping, rape and sexual assault. Nifong dropped rape charges against all three suspects in December after the accuser wavered in key details of her story.
Less than a month later, Nifong, having come under intense scrutiny for his handling of the case, asked the North Carolina Attorney General's Office to appoint a special prosecutor to take over.
"He feels, as a result of the accusations against him, that he would be a distraction and he wants to make sure the accuser receives a fair trial," Nifong's attorney, David Freedman said on Jan. 12. "He still believes in the case. He just believes his continued presence would hurt her."
In February, Durham resident Elizabeth Brewer filed a civil complaint against Nifong that basically mirrors the State Bar's complaint. It is the first complaint from a Durham citizen asking that Nifong be removed from office.
Senior Resident Superior Court Judge Orlando Hudson, however, issued a stay on the complaint until after the State Bar hearing is completed.
Nifong told WRAL on Feb. 9 that he looks forward to defending himself against the charges, which could lead to his disbarment. He added that there is more to the Duke lacrosse case than what the media has reported.
"I wish everyone would withhold judgment until they hear the evidence, as well as my response," he said.
http://www.wral.com/news/local/story/1217557/
"...DNA lab procedures for technicians who handle samples."
It all sounds sensible enough, but the line of reasoning jumps the track upon mention of the word "procedures" in the case of DNA Security!
;)
I believe you have it right as to the DNA evidence although it might have been that Meehan could not be excluded from one of the fragments, ie not a complete match. And it could have come from dander or other tiny cells that fell from him into a sample.