Hm. I see from several posts on this thread that a lot of people don't understand how those pressure switches work.
Here's the important factor: if a light is actuated by a pressure switch, you don't move other fingers around to light it. You simply tighten your grip to turn the light on, loosen it to turn the light off. It's a fast and intuitive system that provides absolutely no possibility of moving your trigger finger a full inch from where it's safely indexed on the frame. It's also far (far!) safer than a flip switch in a similar location, because it requires no real movement of any fingers, trigger or otherwise. Simply a tightening and loosening of one's grip.
On the other hand, if your trigger finger is stupidly resting on the trigger while the firearm is pointed at something or someone you're not willing to shoot, a sneeze could fire the gun for you. So could a cough, getting startled, tripping, a sudden noise, or someone bumping into you. And, of course, tightening your overall grip while your finger is resting on the trigger could become noisy, too.
Knowing these basic facts means we know the problem isn't the pressure switch or its location. It's either
a) the shooter didn't know how to use a pressure switch and tried to use it like a flip switch,
or
b) the shooter thought he was doing such an important job that the safety rules didn't apply to him.
In both cases the solution is training. (Well, and in the second case maybe a dose of humility.)
pax