Scott has put up another great post over at Spartan Cops; it’s called “Why Police Use Locks: Reinforcing Internal Barriers For Officer Safety”. It discusses the various cues that bad guy’s look for when they are contemplating fighting with, or fleeing from, the police.
Many bad guys have similar internal barriers about attacking officers. They are willing to hit most people but not a cop or they are willing to hit a cop but only if they have an opportunity to get away.
Scott’s article then goes on to point out what exactly the bad guy is looking for while he is seeking that opportunity. Well worth a read.