Feinstein says it would be unconstitutional. She is confident a solid case can be made for the death penalty without it.
"There is ample evidence, fingerprinted, I understand, direct testimony from one of the people that had his legs blown off that he recognized him. They admitted to the driver of the car that they hijacked that they were the bombers. So I think there's going to be a great deal of evidence put together to be able to convict him," Feinstein said.
If Tsarnaev is classified as an enemy combatant he could be held indefinitely without trial.
Supporters of the classification believe Tsarnaev may have information about terrorists they can extract from him.