The great majority of violent crime in America goes unsolved
If Trump wants to stop crime in the US, these are the numbers that should worry him.
"Research shows clearly that the chance of being caught is a vastly more effective deterrent than even draconian punishment." They added, "Research has found evidence that prison can exacerbate, not reduce, recidivism. Prisons themselves may be schools for learning to commit crimes." So more certainty of punishment can deter crime, while more severity can actually make it worse after a certain point.