Judith Becker, a professor of psychiatry and psychology, was the second expert witness for the defense. Two court-appointed mental health professionals—testifying independently of either prosecution or defense—were forensic psychiatrist George Palermo and clinical psychologist Samuel Friedman. His skeleton was retained to adorn one side of the private shrine of skulls and skeletons Dahmer was in the process of creating when arrested one week later.

Upon hearing of Dahmer's sentencing, his father Lionel and stepmother Shari requested to be allowed a ten-minute private meeting with their son before he was transferred to the Columbia Correctional Institution in Portage, to begin his sentence. Present at the vigil were community leaders, gay rights activists, and family members of several of Dahmer's victims.He drugged Guerrero with sleeping pills, strangled him with a leather strap, and fellated the corpse. Dahmer had stated in his will that he wished for no services to be conducted and that he wished to be cremated. On May 23, 1989, [139] Dahmer was sentenced to five years' probation and one year in the House of Correction, with work release permitted so he could keep his job. Dahmer dismembered Guerrero's body within 24 hours, again disposing of the remains in the trash and retaining the skull before pulverizing it several months later. Becker diagnosed Dahmer as a necrophiliac, although she added Dahmer had informed her, he preferred comatose sexual partners to deceased ones "75 percent" of the time.

Dahmer drugged Straughter, cuffed his hands behind his back, then strangled him to death with a leather strap.Initially, Dahmer's living arrangements with his grandmother were harmonious: he accompanied her to church, willingly undertook chores, actively sought work and abided by most of her house rules (although he continued to drink and smoke). Upon Dahmer's request, after one year in solitary confinement, he was transferred to a less secure unit, [294] where he was assigned a two-hour daily work detail cleaning the toilet block. For the first year of his incarceration, Dahmer was placed in solitary confinement due to concerns for his physical safety should he come into contact with fellow inmates. Two years later, during a chicken dinner, Dahmer asked Lionel what would happen if the chicken bones were placed in bleach.