TODAY   |  April 30, 2013

Female DNA found on Boston bomb pieces

Law enforcement officials have revealed one of the pieces of the pressure cookers used in the Boston Marathon bombing contains female DNA but they stress it could have come from many sources, including someone who touched it before the area was sealed off. NBC’s Pete Williams reports.

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>>> we are following new information on the boston marathon attacks. female dna found on a piece of one of the bombs, a discovery leading to new scrutiny of the widow of one of the suspects. pete williams is nbc's justice correspondent. pete, good morning.

>> reporter: good morning. law enforcement officials stress the dna could have come from a victim, from someone who touched a piece of the bomb before the area was sealed off or from employees at a store where one of the parts was sold. investigators say they found female dna on one of the pieces of the pressure cookers that were used to build the marathon bombs. experts in bomb investigation say such evidence can actually remain on bomb parts despite the heat and force of an explosion.

>> fingerprints and dna evidence can survive a bomb blast and be recovered from bomb components.

>> reporter: an fbi team conducted a search monday at the rhode island house where tamerlan tsarnaev's widow katherine has been living since the bombing. officials left with a sample of her dna . she said she was shocked by the attack and had no idea he was planning it. in another development law enforcement officials say they found nothing local boston-area landfills but are still searching garbage containers in the belief someone may have carried items out of jdzhokhar tsarnaev's college dorm room. authorities say it's not clear yet whether whoever may have done so knew evidence could be destroyed or did something just to help a friend. as he remains in the hospital his lawyers are talking about a deal to avoid the death penalty in exchange for a full accounting to the fbi of what happened and why. his lawyers added an experienced death penalty attorney, judy clark of california, to his legal team. she represented the unabomber and jared loughner. both pleaded guilty.

>> thank you very much.