The memory of witnesses is crucial in criminal and civil cases, since by itself eyewitness testimony can convict an accused person. Jurors appear to respond more to the confidence with which an eyewitness responds than to the circumstances surrounding the original event and subsequent recollection of it. However, precise memory, which suddenly becomes crucial in the event of a crime or an accident, is rare. The memory is constructed from stored and available bits of information and the gaps are filled in unconsciously by inferences. Furthermore, people who witness fearful events remember the details of them even less accurately. New information can alter a recollection, and the way a question is worded may affect how a witness remembers the event. Moreover, many lineups used in actual cases are suggestive (for example, a black suspect is put in a lineup with all whites). A one-person lineup is especially dangerous, since the image of the person presented might well fuse with a fuzzy, fading memory of the criminal. In controversial cases, one solution is to call a psychologist to testify as an expert witness who can explain how the human memory works and apply experimental findings to the case at hand. A 1980 study shows that jurors regard eyewitness testimony with little skepticism, but the expert testimony serves to increase the likelihood of critical appraisal. A total of 20 references are included.