Authorities say they broke into an apartment to look for prescription drugs in 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" and is best known for his starring role in "A Bronx Tale," says he didn't know Armento had a gun.
Brancato's murder trial is set for Oct. 28. Armento goes on trial Sept. 29.
