Yanez's defense was essentially based on him fearing that Castile was reaching for his gun, the only reason he would have been reaching for his gun would be to shoot Yanez, so yeah, that was his basic assertion.  As I said, ultimately, there really are only 2 people who know exactly what happened, and one is dead and the camera footage doesn't give enough information to determine whether Yanez shot a man for twitching, or for reaching for his wallet, or actually reaching for his gun.  This isn't a matter of declaring open season on the cops, it is  making it clear that none of us know what really happened, except that a guy is dead, the cop and girlfriend have 2 differing stories, and juries tend to side with the police, pretty much, no matter what.