Most employers do nothing when they suspect workers' compensation fraud. But you don't have to be a sitting duck. Here are steps that will unmask fraudulent claims:

* Conduct your own investigation. Talk to witnesses; examine the work site; change it to prevent future harm.

* Audit past claims. Look for patterns that indicate where you can make safety improvements.

* Audit claimants' medical bills. Have the same person who reviews health-insurance bills scrutinize invoices arising from workers' compensation claims.

* Ask your insurer to investigate. The level of investigation undertaken varies widely. Here are some of the probes you should ask your carrier, or a private investigator, to make:

Driving history. Look for any accidents in which an injury might have been sustained and drugs and alcohol might have been involved.

Employment record. Ask for a record of prior claims from the workers' compensation claims division of states in which the employee previously worked. Also check claims under appeal, sometimes filed separately.

Credit history. Because fraudulent claimants often moonlight while collecting benefits, checking a credit history is "the biggest clue" to fraud, notes Dave Orlebeke, president of private investigator ASO, in Newberg, Oreg. Much of this information is protected by the Fair Credit Reporting Act, so observe the law in getting it.

* Report claims to the state. Report claims to your state's department of revenue to prevent a worker from collecting unemployment insurance as well as workers' comp payments.

Whatever information you can collect should be presented to the claims department of your carrier, which will decide if it should fight the claim. Also, express ongoing interest in the carrier's investigation. -- Ellyn E. Spragins