Three dozen people have been charged with scheming to defraud automobile insurers out of more than $279 million in accident benefits, in a scheme said to involve doctors, lawyers and patients who were coached to fake injuries. Federal and New York City investigators said the defendants took part in a "medical fraud mill" involving bogus clinics in and around New York City that billed insurers for unnecessary or nonexistent treatments. They said the ring was designed to exploit New York's "no-fault" auto insurance law, which requires vehicles registered in the state to carry insurance that lets drivers and passengers obtain up to $50,000 for accident injuries, regardless of fault.