the theory is that in times of extreme stress fumbling with the external safety officers have discharged the weapon when they were not ready. With a Glock that cannot happen since the trigger is the safety. It is a good design but requires training. I carry a Glock due to its light weight but I still liked the external safety that a colt had. The cocked and locked worked for 90 years. Without proper training people have shot themselves in the leg by holstering the gun and having their finger on the trigger when they do it ... never touch any trigger unless you are going to shoot but officers have forgot that rule. With a glock it even more of a rule. One of the NFL guys Burris just found that out, carried an illegal weapon in New York and just got 2 years in prison for having an illegal weapon ... shot himself in the leg ... yup a glock ... too bad huh ... had no legal right to have it and no training on it either. He deserved what he got