10-Ring
I work as a paramedic. We had a class about six months ago that included some stuff on these shotgun bean bag rounds. It turns out that they are certainly lethal. We saw the autopsy photos to prove it. The main problem is that they are not to be fired at point blank range. I don't remember the distance, but obviously when the officer needs to use one, he doesn't stop and measure how far away he is. For example, there was one photo of a guy that was wearing a big madallion around his neck. The bean bag impacted the madallion and drove it clear through his chest. There have also been some deaths resulting from blunt trauma to the chest where the bean bag did not enter the chest wall, but caused fatal internal injuries from the blunt trauma from being fired too close to the victim. Another issue, if I remember correctly was that the bag was sewn together with a teflon cord. If the bag struck on the side, this cord cut through flesh like a knife.
These problems have been dealt with here locally. They went to a different bean bag round that is supposed to take care of the teflon thread issue. The local PD was in the process of shooting up all the old rounds in training.
Another factor is that if you start using different shotgun shells for different purposes, you might become confused as to what you have loaded. You might have a bean bag loaded when you need the real thing, or you might have the real thing loaded when you thought it was a bean bad. The police overcome this problem by using designated shotguns for bean bag rounds. The guns are orange in color and never had standard shells fired though them.