Originally Posted by orangello
I'm betting the beat cops carrying these didn't make the decision to bob them; it was probably paranoid administrators hoping to dodge a bad shoot.
A long time ago, I seem to recall someone laying the blame on lawyers. The arguement was based or revolved around the "intent" of the shooter. If the hammer was cocked prior to shooting, then the shooter's intent was deliberate. Maybe even premeditated or why else would he have cocked the hammer in the first place ? (Forget about accuracy & reality for a moment - this is about a lawyer "working" a jury.)
Since single action is a significantly lighter pull, the discharge may have been accidental or maybe even negligent in a tense situation.
Double action was not given the same level of scrunity. Allegedly, experts were called in to determine if the shot was SA or DA based on depth of primer strike. (Not even sure it's possible)
To remove the possibility of litigation, hammers were bobbed to make SA fire impossible.
Then again, this may just be an urban myth. I live in New England and as Mark Twain once said, "Never let the truth get in the way of a good story."