Trying Tsarnaev in civilian courts -- like "hundreds of terrorists" to date -- is "absolutely the right way to go and the appropriate way to go," Carney said. "We have a long history of successfully prosecuting terrorists and bringing them to justice, and the president fully believes that that process will work in this case."
That disappointed Sen. Lindsey Graham, R-South Carolina, who has been calling for Tsarnaev to be handed over to U.S. intelligence as an "enemy combatant."
"There is ample evidence here on the criminal side," Graham said. "A first-year law student could prosecute this case. What I am worried about is, what does this individual know about future attacks or terrorist organizations that may be in our midst? We have the right to gather intelligence."
Graham also said there was also "ample evidence" that the bombings were "inspired by radical ideology."
But while Tamerlan Tsarnaev apparently became increasingly radical in the past three or four years, according to an analysis of his social media accounts and the recollections of family members, there was no evidence Monday that he had any active association with international jihadist groups.
Tamerlan Tsarnaev, 26, died after a shootout with police early Friday. Dzhokhar Tsarnaev was captured that night, after police found him hiding in a boat in the back yard of a house in the Boston suburb of Watertown, Massachusetts.
Older suspect's wife
With one suspect dead and the other hindered in his ability to communicate, investigators are eager to speak to Tamerlan Tsarnaev's wife, Katherine Russell, to see what she might know about incidents leading up to the bombings.
On Monday, her attorney said she learned of her husband's alleged involvement through news accounts.
"She knew nothing about it at any time," Amato DeLuca said in response to questions about whether Russell knew of plans to attack the marathon.
Tsarnaev stayed home and cared for the couple's 2-year-old daughter while his wife worked long hours as a home-care aide, according to DeLuca.
The family is devastated, the attorney said.
"They're very distraught. They're upset. Their lives have been unalterably changed. They're upset because of what happened, the people that were injured, that were killed. It's an awful, terrible thing," he said. "And of course (for) Katy, it's even worse because what she lost -- her husband and the father of her daughter."
Clues about radicalization?
The Tsarnaev family hails from the Russian republic of Chechnya and fled the brutal wars there in the 1990s. The two brothers were born in Kyrgyzstan; Dzhokhar became a U.S. citizen in 2012, while Tamerlan was a legal U.S. resident.
An FBI official said agents interviewed Tamerlan Tsarnaev in 2011 at the request of the Russian government. The FBI said Russia claimed that he was a follower of radical Islam and that he had changed drastically since 2010.
But the Russian government's request was vague, a U.S. official and a law enforcement source said Sunday. The lack of specifics limited how much the FBI was able to investigate Tamerlan, the law enforcement official said.
In August 2012, soon after returning from a visit to Russia, the elder Tsarnaev brother created a YouTube channel with links to a number of videos. Two videos under a category labeled "Terrorists" were deleted. It's not clear when or by whom.
Tamerlan Tsarnaev attended prayers periodically at the Islamic Society of Boston's mosque in Cambridge, a board member told CNN's Brian Todd. In a statement issued Monday, the society said he twice interrupted sermons -- once in November to express his opposition to celebrating any holiday as un-Islamic, and once in January when he tore into the preacher for citing civil rights leader Martin Luther King.
The second time, the congregation shouted back, "Leave now," the statement said.