In this case witnesses and victims are under hypnosis and as they are asked questions about a certain scene they are said to be able to enhance their memory due to hypnosis. This enhancement of memory using hypnosis is known as hypermnesia.
There have been doubts about the recall of memories recalled in this way. It is said that whilst people are under hypnosis the relaxation they feel can help them in memory recall.
We will now look at some studies with the use of hypnosis in memory recall to see the results and find out just how effective hypnosis is.
Putnam (1979) showed participants a video of an accident involving a car and a bike. Half of the participants were hypnotised. He asked misleading questions and found that the hypnotised participants made more errors especially with respect to misleading questions. Here overall there was increases recall but due to confabulation more errors were made. This shows that when people are hypnotised they could make mistakes with vital information, which in the end would not be trustworthy.
Green and Lynn hypnotised participants and asked them if they had heard a loud noise during a nights sleep (none of them had). Some of the participants were warned that hypnotism can lead to false memories. With the participants that were not warned 44% said that they had heard a noise whereas in the warned group only 28% did. This shows that implanting false memories while people are hypnotised can lead to false memories.
Just by looking at these two studies a lot can be said of the use of hypnotism in memory recall. First of all the fact that there are not many studies on hypnotism and its effectiveness can only show that it is a rather weak tool. Also what does it mean for someone to be hypnotized? No one really knows. Are people in a trance or are they asleep. It is physiologically impossible to tell. When hypnosis does work it could be because of a relaxed setting victims and witnesses are in that helps.
Hypnosis can also be analysed in terms of ethics. The fact that they are making through the trauma they may have gone through may force to say something incorrect to avoid having to deal with what has happened.
There is not sufficient evidence in the use of hypnosis so would say leave it behind.