Forensic examination of bomb remains in the Boston blasts has indicated the presence of “female DNA”, said law enforcement officials on Tuesday, even as questions were raised about whether the surviving suspect, Chechen-origin Dzhokhar Tsarnaev (19), was denied his constitutional right to a lawyer after his arrest.

Though it points to the possibility of the Tsarnaev brothers having taken outside help for the attack, authorities said the DNA could have come from unconnected source, for example: a store cashier.

Reports said that FBI officers were “collecting DNA samples from some women who were close to the pair to provide a comparison”. Officials also said the material could have come from “a stray hair... that unwittingly ended up on the explosive devices”.

The news came even as The Los Angeles Times reported that the FBI had actually interrogated Dzhokhar for a full 16 hours prior to reading him out his “Miranda rights”.

The newspaper also reported that rather than reading Dzhokhar his Miranda rights out of respect for due process, the High Value Detainee Interrogation Group halted its interrogation when a federal magistrate independently scheduled a hospital-room hearing. Dzhokhar has since been read out his rights and chosen to go silent.

Defence team

It was confirmed this week that Judy Clarke, described as “a San Diego lawyer famous for getting life sentences instead of the death penalties for her clients”, had joined the defence team after her appointment was endorsed by U.S. Magistrate Judge Marianne Bowler.

Previous clients of Ms. Clarke include Jared Lee Loughner, charged with carrying out the deadly public shooting in Tucson, Arizona in January 2011, and “Unabomber” Ted Kaczynski, the former mathematician who was convicted to life in prison after being held responsible for a series of bombings between 1978 and 1995.

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