Many crimes are committed by repeat offenders so it would eliminate a decent chunk of crime. Over 60% of violent criminals in the US get rearrested for another crime. Almost 40% of nonviolent criminals get rearrested for another crime.

If they stop committing crimes either because they are still in jail or dead, the crime rate would absolutely drop.

https://www.ussc.gov/research/research-reports/recidivism-am...