Defendant was denied his Sixth Amendment right to effective assistance of counsel when his attorney failed to request a diminished capacity jury instruction. At trial, defendant testified that he committed two murders; the only issue in dispute was whether he acted with premeditation. Defense counsel presented substantial evidence through expert testimony that defendant lacked the capacity to premeditate because, at the time of the murders, he suffered from a right temporal lobe seizure, or “explosive dyscontrol,” from chronic drug use. Nonetheless, counsel did not request a diminished capacity instruction, which would have allowed the jury to consider whether Pirtle’s mental condition affected his ability to premeditate. Instead, counsel requested an intoxication instruction. This instruction constricted the jury’s consideration of the evidence relating to premeditation to the narrow issue of whether Pirtle was in a state of voluntary intoxication when he committed the murders.