NEWARK, Aug. 20 (AP) - The authorities on Friday questioned the mental competence of a doctor who told reporters this week that he had had an affair with the man accusing Gov. James E. McGreevey of sexual harassment. A state judge said he found a "pattern of aberrant behavior" and ordered a psychiatric evaluation for the doctor, David Miller, 51, who was arrested on Thursday night on unrelated charges, including impersonating an F.B.I. agent. County law officers said their investigation had begun before Wednesday, when Dr. Miller told news organizations that he had had an affair with Golan Cipel,...