Leonard Scalzo and his wife, Denise, testified they had just gotten home from work and saw Patrolman Christopher Matlosz drive up to a young man near their house. They both described watching the suspect pull out a gun, lean into the patrol car and fire three shots.
The husband identified Jahmell Crockam in court as the shooter. His wife was not asked to identify the defendant.
The 20-year-old is accused of gunning down the 27-year-old officer in 2011.
Crockam's lawyer says police arrested the wrong man and questions the reliability of the witnesses.