In the case of Tsarnaev, there are other potentially complicating factors at play for the federal government in Massachusetts, a state long opposed to the death penalty.

In September, less than six months after the attack, a poll commissioned by The Boston Globe found that 57% of Boston residents favored Tsarnaev’s facing life in prison without parole, while only 33% supported death. The opposition, in the city deeply scarred by the bombing, crossed political lines with Democrats overwhelmingly favoring life in prison at 61%-28% and Republicans more narrowly supporting prison over death at 49%-46%.

“It’s one thing for the government to be willing to impose the death penalty; it will be a lot harder to find people in Massachusetts to serve on a jury who would vote for the death penalty,” said Andrew Smith, director of the University of New Hampshire Survey Center, which conducted the poll. “It’s not terribly surprising given that it is Massachusetts.”