The last time a New Hampshire court imposed a death sentence was in 1959, but the two condemned men were spared by a 1972 U.S.
Supreme Court ruling. New Hampshire last executed someone in 1939, has no one on death row and has no death chamber.
The judge must impose the sentence and cannot change it.
Addison's lawyers argued that his abusive childhood and possible brain damage from his mother's heavy drinking while she was pregnant warranted a sentence of life in prison without parole.
Addison had been on a crime spree the week before the shooting and had said he would "pop a cop" if necessary to avoid arrest.
Briggs, 35, and his bicycle patrol partner came across Addison and friend Antoine Bell-Rogers walking in an alley early on Oct. 16, 2006. Briggs recognized the men as a suspects in a recent shooting and two armed robberies and ordered them to stop. Addison turned and shot Briggs in the head at close range, testimony showed.
The defense admitted on the first day of the trial that Addison killed Briggs, but said the act was reckless, not intentional.
"It was fast and it was totally unplanned," defense attorney David Rothstein said in his opening statement. "It was a reckless act that ended in a terrible tragedy."
Prosecutors called the shooting cold-blooded and premeditated, pointing to Addison's threat to "pop a cop."
"That fatal shot was no accident. It was no reckless misjudgment or panic-driven mistake," Attorney General Kelly Ayotte said in her opening statement.
The state Supreme Court will automatically review the conviction and sentence. If the court upholds both, an appeal by the defense is virtually certain, likely raising constitutional claims rejected by the judge. Among them is that Addison couldn't get a fair trial in Manchester, and that requiring judges to impose a death sentence decided by a jury is unconstitutional.
Legal experts note that New Hampshire's death penalty law, unlike laws in states such as Texas, has not been tested extensively in court.