To answer the original question, if what I think you are trying to find is this: does a handgun cocked (revolver, model 1911) and ready to fire in a single action mode lead to more accidental shootings than a handgun (revolver or semi-auto) that is to be fired in a double action mode inwhich the trigger pull is heavier and the trigger must travel a farther distance.
Logic would tend to sugest YES. In the panic of the moment I think a shaking finger on the trigger- pointed at a perp- might accidentally set off the firearm. Everyone has their own feeling on this, the single action is more accurate- that's for sure- but in a home invasion, at a very close range- I think a 6" barrel model 19 S&W in 357 magnum, to be fired double action, would be a very good choice for most people. That is probably how they ought to practice at the range.