Where the trial court had before it substantial evidence that the developmentally-disabled defendant could not understand the nature of the proceedings or assist in his defense, the court’s failure to institute competency proceedings under Penal Code section 1368 deprived the defendant of his constitutional right to a fair trial. In litigating the admissibility of defendant’s pretrial statements to investigators, the defense had provided substantial information regarding defendant’s disability and his inability to understand the proceedings, including evidence that his IQ was between 45 and 59, that his academic abilities were in the range of early kindergarten levels, and that he was unable to assist his lawyer because of his extreme memory problems. Under these circumstances the court below should have instituted competency proceedings on its own motion. The appellate court rejected the People’s argument that the defense invited the error, noting that competency issues cannot be waived by counsel. Finally, the court held that under the unique circumstances of this case, where the record contained substantial evidence regarding the defendant’s mental state at the time of trial, a retrospective competency hearing might be appropriate. The court thus remanded the matter for the trial court to determine whether the available evidence and witnesses are sufficient to permit the court to reach a reasonable psychiatric judgment of the defendant’s competency at the time of his trial. At this hearing, the People will bear the burden of showing that sufficient evidence exists for the trial court to retroactively determine the defendant’s competency.