Modifies provisions relating to trial procedures for murder in the first degree

HB 452 modifies Missouri's trial process for first-degree murder cases where the death penalty is sought. It requires a two-stage trial: first determining guilt, then deciding punishment. If the jury finds the defendant guilty but does not impose death, they must sentence to life without parole under specific conditions (intellectual disability, no aggravating circumstances, or mitigating evidence outweighing aggravation). This applies to defendants in Missouri murder trials where the death penalty was not waived, effective for offenses committed on or after August 28, 2001.