Violent crime rates have gone down in part due to the disappearance of lead in the environment. Lead, an insidious poison, created behavioral pathologies and learning disabilities. Bullet-proof vests have made it less likely that a crook shoots a cop and gets away for a few hours only to get caught soon afterward. Cop-killers were a big part of the number of death sentences. Crooks trying to shoot it out with the police are now more likely to be killed by cops than survive to face capital-murder charges. Better police work makes it less likely that violent offenders get away with extended crime sprees that might culminate in a robbery-murder.
