The Ohio and Michigan units both claim conviction or guilty-plea rates of better than 90 percent -- about the same as for other Federal indictments in the jurisdiction. In addition to crooked M.D.s, the two anti-fraud units have nailed optometrists, chiropractors, pharmacists, and podiatrists over the past 12 years. Most investigators start with a tip, usually over a toll-free antifraud hot line that each of the two Blue Shield plans maintains. After a tip, the insurance cops scrutinize claims and reimbursements to see if further investigation is warranted. A strong circumstantial case is already built before the cops go undercover. Some states forbid the use of hidden tape recorders to collect evidence so investigators use stakeouts and interviews, making careful notes and reports after each phase of an operation. Fraud investigators rely entirely on an unscrupulous physician's greed and desire to steal. Full restitution for the money that is stolen is seldom recovered, however, the objective is to protect the insurance subscribers, stop the losses, and deter miscreants. In the 6 years since the Ohio unit was started, it has helped indict 166 individuals and corporations for defrauding Blue Shield of nearly $16 million.