Gregory Ulas Powell, imprisoned for murdering Los Angeles Police Officer Ian Campbell in a Kern County onion field in 1963, should be paroled, his lawyer told the state Supreme Court. In asking the court to take the unusual step of overturning a state Board of Prison Terms decision, lawyer Dennis Riordan said the board had no legitimate reason in 1982 to revoke Powell's parole date of October, 1983. Riordan said the board relied on a flimsy report by a psychiatrist, who never examined Powell, and an unproven charge by a prison guard that Powell had sex with his daughter during a prison visit. Deputy Atty. Gen. Dane Gillette said the board acted within its authority to overturn the earlier board's decision to grant Powell's release. The justices' decision is not expected for at least another six months.