A convicted killer maintained his innocence Tuesday at the opening of his second murder trial, saying he’s not the masked armed robber who fatally shot a 7-Eleven store clerk in Columbia.

Charles Richardson, 26, who was convicted Oct. 2 of killing a Columbia teen, now faces charges in the April 2007 slaying of Alevtina Zhilina at a convenience store across the street from Richardson’s apartment on Columbia Road — a crime in which prosecutors could have sought the death penalty.