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

This bill changes Missouri's trial process for first-degree murder cases when the death penalty is not waived. It requires a two-stage trial: first, a determination of guilt (without punishment), followed by a separate stage to decide sentencing. A life sentence without parole becomes mandatory if the jury finds intellectual disability, no aggravating factors exist, or mitigating factors outweigh aggravating ones. The law applies to cases filed after 2001 and mandates resentencing for some prior death-sentence cases before August 2026.