Hypnosis is no aid to justice

''The use of hypnosis to 'assist' the memories of witnesses has become increasingly common. This practice depends on questionable assumptions.''

So warns Ulric Neisser, a Cornell University psychologist. He sees considerable danger in this practice, which now is used widely by police in the United States and has even entered into some court cases.

Neisser explains: ''It (hypnotically assisted memory) assumes the existence of automatically established, fully accurate, and permanent memory traces; it also assumes that the hypnotized witness carries out a direct and unbiased inspection of those traces. Neither of these claims can be sustained in the face of what we now know about memory and hypnosis. The results of psychological research suggest that current practices are ill-advised.''

This sums up the serious reservations that many psychologists have about the use of hypnosis in police work and especially in cases brought to trial. Not all psychologists or practitioners of hypnotism agree. Some consider hypnotism, when carefully used, to be a useful tool in jogging the memory of witnesses who may suffer a mental block. There is wide agreement, however, that careless use of this tool can be dangerous. Under the influence of hypnotic suggestion, witnesses can be led to believe they saw what, in fact, they did not see.

Neisser and several other experts presented these dangers at a session of the annual meeting of the American Association for the Advancement of Science earlier this year. The liabilities would seem to far outweigh any supposed benefits.

For example, the benefit of hypnosis is often illustrated by citing such cases as that of the California children kidnapped from a school bus in 1976. Hypnosis was credited with aiding the bus driver to recall enough of the getaway van's registration number for police to locate it.

Balanced against these cases are potential fiascos such as that described by Martin T. Orne of the University of Pennsylvania. He told how a hypnotized witness recalled the face of a murderer, implicating a specific person. Brought to trial on the strength of that testimony, that person probably would have been convicted, Orne said, if an optical expert had not proved it to have been impossible for the witness to distinguish a face at the distance specified (about 100 yards) under the foggy conditions that prevailed at the time.

Memory is fallible and likely to be modified by information learned after the fact. Orne said that, under hypnosis, a witness is liable to further corrupt memory, substituting fantasies or suggestions for his own recollections. What is worse, he warned, hypnosis can induce a false sense of certainty about these fallacious memories.

Orne, Neisser, and other concerned psychologists say that strict safeguards are needed if hypnosis is used with witnesses. But would any safeguard truly be adequate? While hypnosis is of questionable value in police investigation, certainly it should have no place at all in a court of law.