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

This bill modifies trial procedures for first-degree murder cases in Missouri by separating the guilt phase from the punishment phase when the death penalty is sought. If a defendant is found guilty, the trial proceeds to a second stage where the jury or judge decides on sentencing based on evidence regarding aggravating and mitigating circumstances. Under the new rules, a defendant will automatically receive life imprisonment without parole if the trier determines they are intellectually disabled or if they do not meet the specific criteria required for a death sentence. The legislation also allows for intellectual disability to be resolved before the trial begins if both parties agree, and it applies these changes to offenses committed on or after August 28, 2001.