Forty students served as subjects in two groups of witnesses to which a surprise filmed crime was shown. All subjects gave free recall statements about the crime. Following either a directed thinking interval or a diversionary task to block rehearsal, witnesses gave two additional statements. Hypermnesia for hits and memory intrusions was observed, but d' scores did not show hypermnesia. The witnesses fell into two groups: "good" witnesses who had ascertained the correct schema and "bad" witnesses who were obviously on the wrong track. While most witnesses showed short-term hypermnesia for correct responses (hits), the good witnesses showed a significant increase in memory intrusions (false alarms) during the third recall trial (p < .01). Only with correct-schema witnesses did d' scores above the guessing level occur. Witnesses who had ascertained the correct schema but who were interrogated too often tended to make things up to suit the demands for detail, with a resultant increase in memory intrusions and lower d'.