For at least 50 years, there have been calls to replace, or at least supplement, expert witnesses hired by courtroom adversaries with experts appointed by the court. According to advocates of those proposals, the judge-picked scientist could focus on the evidence and advise the jury free from pressures imposed by the side that hired him. Judges in Kentucky already are allowed to appoint their own experts, but they almost never do. Dr. Ralph Slovenko, professor of psychiatry and law at Wayne State University, says court-appointed experts haven't caught on because judges are reluctant to tamper with the adversarial process.