Blumstein and his colleagues argue for controlled experimentation as the ideal approach to test for any effects, including those of deterrence. Such studies provide strong evidence for or against deterrence of a given behavior, so as to inform the potential consequences of public policy in impacting undesirable behavior. Such an approach was used in an effort to determine the deterrence realized by a policy to counter auto repair fraud in a California community. In the experiment, women were sent to randomly selected repair facilities in two matched California metropolitan areas. The women explained that they were preparing to move from the area and their cars would not start. They brought their car batteries with them to be tested by the shops. Since the batteries were known to be good, the test of honesty involved whether or not the shops would recommend the purchase of a new battery. The experimental area was then subjected to an intervention designed to increase perception that unpleasant legal consequences were likely to follow from fraudulent auto repairs. Post-tests were run following the intervention for both the experimental and control areas. Initial analysis suggests that a deterrent effect may have been accomplished. Forty-one references are provided.