In addition to Mr. Breckinridge, a number of people here, including some lawmakers and two former state attorneys general, have publicly changed their minds on the matter.

Representative Stephen Shurtleff, a Democrat and former United States marshal who in 2010 favored keeping the death penalty, said this time that the penalty was “a barbaric practice” and that making convicts sit in prison every day and think about what they had done was a worse punishment than ending their lives.

Others said they believed that the death penalty had been applied unequally, with Mr. Addison, who is black, sentenced to death but a white defendant in another murder case given life without parole.

Supporters of the death penalty argued that unless certain murderers were put to death, they could escape and kill again. They also said that prosecutors needed the death penalty as a bargaining chip. And, they said, New Hampshire was already a difficult state in which to get the death penalty because of a lengthy checklist of conditions that must be met.

“This is not Texas,” said Representative Keith Murphy, a Republican who supports the death penalty. “We are not executing prisoners every week.”

The state has one person on death row — Mr. Addison, who was sentenced to death in 2008 for the murder of Mr. Briggs. His case is expected to cost at least $8 million as he appeals; the annual cost here for someone in prison for life is $35,000.

“People have had a change of heart because the more they see how it works in the Addison case, the less they like it,” said Arnie Alpert, spokesman for the New Hampshire Coalition to Abolish the Death Penalty.