CONCORD, N.H. (AP) — New Hampshire's top court upheld the sentence of the state's only death row inmate, clearing the way for a convicted cop killer to become the first person executed in New Hampshire since 1939.

Michael Addison, 33, was convicted of gunning down Michael Briggs in 2006 as the 35-year-old Manchester police officer was attempting to arrest him on a string of armed robbery charges.

The high court's unanimous ruling came nearly a year after it heard unprecedented daylong arguments in the first death penalty appeal to come before it in 50 years.

Addison's lawyers argued that holding the trial in a courthouse a stone's throw from the Manchester police department injected passion and prejudice into the jury's verdict.

"The watershed event in this case was not moving the trial out of that courthouse," attorney David Rothstein argued.

But the Supreme Court disagreed, upholding the trial court's finding that police headquarters is a "non-descript" building and a memorial to Briggs is barely visible to the public.

Prosecutors countered that both sides worked hard to guarantee Addison a fair trial and that jurors certified their verdict was not influenced by arbitrary factors.

"We conclude that the sentence of death was not imposed under the influence of passion, prejudice or any other arbitrary factor," the justices wrote.

Of all 22 issues raised by Addison's lawyers on appeal, the justices concluded, "We find no reversible error."

The Supreme Court will next schedule arguments on its fairness review — weighing Addison's sentence against those meted out in 49 cases around the country between 2000 and 2009 in which a police officer was shot in the line of duty.

Addison's lawyers objected to the scope of the comparison, saying it ignores the only other New Hampshire capital case in recent history. That case involved a wealthy white man — John Brooks — who plotted and paid for the killing of a handyman he thought had stolen from him. Brooks was spared a death sentence in 2008 — the same year Addison was sentenced to die.

Addison's lawyers — Rothstein and Richard Guerriero — issued a brief statement saying they disagree with the court's ruling and look forward to addressing the fairness of his sentence.

Attorney General Joseph Foster said the magnitude of the court's 243-page ruling is appropriate given the magnitude of the loss suffered by the Briggs' family. He did not comment on the ruling itself, noting that aspects of the case remain pending.

Briggs was 15 minutes from the end of his shift on Oct. 16, 2006, when he and his partner — both on bicycle patrol — confronted Addison in a dark alley. Jurors found that Addison shot Briggs in the head at close range to avoid arrest.

Addison was later convicted of going on a violent rampage in the days before Briggs' death, including two armed robberies and a drive-by shooting.

Because it was the first death penalty appeal in decades, the justices had to first determine the pool of cases to compare with Addison's to determine whether his sentence was influenced by race or other factors. Addison is black; Briggs was white.

The last person executed in New Hampshire was Howard Long, an Alton shopkeeper who molested and beat a 10-year-old boy to death. He was hanged — still a viable form of execution in New Hampshire if lethal injection is not possible.

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