By Richard Valdmanis
BOSTON (Reuters) - New Hampshire's top court on Wednesday upheld a capital conviction for cop-killer Michael Addison, but said his death sentence was still under review.
Addison became New Hampshire's only death row inmate in 2008 and would become the first prisoner in the state to be executed in more than 70 years if his sentence is upheld.
State Supreme Court Chief Justice Linda Dalianis dismissed an appeal by Addison's attorneys seeking a mistrial. They argued the process was marred by technical errors and questions over the constitutionality of capital punishment.
"We affirm the defendant's conviction for capital murder," Dalianis wrote in a court filing. "The sentence of death was not imposed under the influence of passion, prejudice or any other arbitrary factor."
Dalianis said the court still had to hear arguments on "comparative proportionality" before making a final decision on whether to uphold Addison's sentence.
Comparative proportionality reviews are aimed at determining whether the sentence is in accordance with other punishments doled out for similar crimes in other cases.
Addison, 33, was convicted of shooting a Manchester bicycle policeman, Michael Briggs, in 2006 as Briggs was trying to arrest him following a string of robberies and a gunfight.
The case revived the debate about capital punishment in the New England state, which has not executed a prisoner since 1939.
State lawmakers' efforts to repeal or weaken the death penalty repeatedly have been quashed by governors' veto powers, most recently in 2009.
Addison's appeal comes as support for the death penalty nationwide has been flagging.
A Gallup poll released last month showed 60 percent of Americans favor capital punishment for convicted murderers, the lowest percentage since 1972, and down from a peak of 80 percent in the mid-1990s.
(Editing by Scott Malone and Bob Burgdorfer)