H.B. No. 688 amends the Code of Criminal Procedure to establish that individuals with an intellectual disability cannot be sentenced to death for capital offenses. The bill introduces Chapter 46D, which outlines definitions related to intellectual disability, including "deficits in adaptive behavior," "developmental period," and "significantly subaverage general intellectual functioning." It mandates that a defendant's attorney can request a hearing to determine if the defendant has an intellectual disability, with specific timelines for when this hearing must occur. The burden of proof lies with the defendant to demonstrate their intellectual disability by a preponderance of the evidence.

Additionally, the bill stipulates that if a jury is empaneled to determine the defendant's intellectual disability, their verdict must be unanimous. If the jury finds the defendant to have an intellectual disability, the judge must issue an appropriate order. Conversely, if the jury does not find the defendant to have an intellectual disability, the trial will proceed as if the hearing had not occurred. The bill also allows for a judge to conduct the hearing without a jury if the defendant waives that right. The changes will apply to trials commencing on or after the effective date of the Act, which is set for September 1, 2025.