Authorities said the two broke into an apartment to look for prescription drugs in December 2005. Officer Daniel Enchautegui confronted them and was killed in a shootout. Armento is accused of firing the fatal shot.
Brancato, who played an aspiring mobster on HBO's "The Sopranos," says he didn't know Armento had a gun.
"I know in my heart I was in no way responsible for the death of that police officer," he told CBS 2HD.