As told by Police trainer Ken Murry...
Take 5 apes and put them in a large cage. In the center of the cage put a staircase.
Hanging from the top of the cage, put a banana hanging from a string. Arrange it such that whenever an ape steps on the top step to get to the banana a hose showers all the other apes with water. Eventually the apes will learn not to try to get the banana because they all get wet. They just will let it be.
Now, remove one ape and put a new one in. He will see the banana and try to get it, but as soon as he heads for the stairs the other 4 apes will beat the crap out of him, because they don't want to get wet. Eventually the new ape will learn not to climb the stairs. You can disconnect the hose at this point.
Change one of the remaining 4 original apes for a new one, leaving 3 original and 2 new. When the newest ape tries for the banana, the other apes will beat the crap out of him. The last one you changed out will participate in the beating because he wants to fit in and can't believe this idiot newcomer doesn't know the rules.
Continue to change out all the original apes, one by one, until you have 5 new apes. They will never go for the banana, and beat up any newcomers who try, and the only reason is because “That’s the way it’s always been around here.”
Just because “that’s the way it’s always been …” is insufficient reason to preserve the status quo of a law enforcement training program.