The boy was lured into an alley and shot to death back in November 2015 near Dawes Park in the Auburn Gresham neighborhood
Prosecutors say Dwright Boone Doty shot the boy execution style while Corey Morgan watched in a nearby getaway car.
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On Monday, an informant testified that Doty talked about the murder of Tyshawn Lee all day every day in the jail.
Last week Jalen Anderson, who was 14 at the time, testified in court. He said he was in the area when Tyshwan was killed and saw a man carrying a gun.
Closing arguments could begin as early as Thursday.