Although Jennifer Lauro, cochair of the employment practices group at Peabody & Arnold LLP, in Boston, is skittish about personality tests, she says she's never actually taken a case involving them to court. "But I'd be very surprised if these tests weren't biased in one way or another," she says. Michael Delikat, cochair of the employment law department in the New York office of Orrick, Herrington & Sutcliffe, agrees that psychometric tests are fraught with potential problems. "There have been a number of challenges, some of them successful," he says. For example, there have been discrimination-based claims, usually concerning "ability" or "aptitude" tests.

As with any human resources policy, to use tests effectively you need to take some reasonable precautions:

Ask for a warranty of indemnification. One way of making sure you're dealing with a reputable testing outfit, says Delikat, is asking for a signed agreement stating that the testing company will reimburse you for any legal muddle. You probably won't get it, but it can't hurt to ask.

Avoid tests that reveal physical or mental impairments. The Americans with Disabilities Act (ADA) limits the use of medical tests by prospective employers before a job offer is made. Make sure the test wasn't intended to expose such medical conditions as schizophrenia and manic depression, both covered by the ADA.

Check your state's privacy laws. About 10 states -- California, for one -- have some sort of privacy protection in their constitution. Should an employee refuse to participate, don't take disciplinary action against him or her, says Lauro. "If that employee is terminated, he or she might make some sort of privacy claim," she says.

Measure your hiring impact on subgroups. Keep records to see if the process appears to affect certain groups more than others. If it does, it could appear as if you're targeting them.