3. Forens. Sci. Soc.
(1977), 17, 77
The Use of Hypnosis in Police Investigation: A Preliminary Communication M. KLEINHAUZ, I. HOROWITZ and Y. TOBIN Headquarters Israel Police, Investigation Department, Criminal Identijcation Division, Jerusalem, Israel.
Hypnotic techniques were used in criminal investigations in order to improve the memory of forty subjects who were involved either as witnesses or complainants. The evaluation of the experience in these cases indicate that hypnos:'~may be a potential tool to elicit essential information from cooperative subjects. It was found that the amount of information elicited through hypnosis increased with the meaningfulness of the material to be recalled and the leuel of anxiety it involved. Some requisites for the use of hypnosis in police investigations are suggested. Introduction Although there is controversy concerning the theoretical foundation of hypnosis, there is much agreement among scientists concerning the ways in which the hypnotic state can be induced, and the changes in human behaviour as a result of hypnotic suggestion. For many years, hypnosis has been used by clinicians interested in facilitating their patients' recall of previously forgotten or suppressed material. Psychotherapists usually achieve hyperamnesia (memory recall greater than that achieved in a non-hypnotic state) using age regression, and revivication techniques. Age regression is when the subject is "brought back" in time and made to recall situations of his past life. With revivication the subject is made to relive, or re-experience, earlier events of his life, and all memories subsequent to the point to which he is regressed are erased. A review of the experimental literature dealing with memory recall under hypnosis shows that significant improvement occurred only for meaningful material. Stalnaker and Riddle (1932) reported a significant recall of prose and poetry learned at least one year earlier. Rosenthal (1944) found significant hypnotic hyperamnesia using poetry, and True (1949) reported improved recall when subjects were asked to recall the day of the week in which their birthday fell in the particular year to which they were given regression suggestion. However, Mitchell (1932), and Barber and Calverley (1966), found no improvemefit with hypnosis in the recall of nonsense material. Kroger (1963) adds another variable stating that it seems that whenever some emotional factor interferes with the recall of stored information, hypnosis will be an effectual tool to achieve hyperamnesia. Following a comparative study of recall in hypnosis, Rosenthal (1944) reported finding that in the absence of effective factors, hypnosis does not favour "recall of meaningless material, or of meaningful material which is not part of our organized context". On the other hand, he finds hypnotic hyperamnesia for some experiences of an emotionally disturbing nature and for contextual material. Case Reports The Scientific Interrogation Unit of the Israel Police began using hypnotic techniques in 1973. I t was found that much relevant information perceived at the scene of a crime was later forgotten, and eye witnesses and complainants were unable to report crucial facts and details. This forgotten material may
include descriptions of suspects, vehicles, licence numbers, weapons, etc. Hypnosis was used in order to enhance the memory of eye witnesses and/or complainants. Criminal investigations in which hypnosis has been used can be divided into three major categories :a) Cases in which it was assumed that the loss of memory was due to a motivated repression of details and/or events evoking overwhelming anxiety: Case No. 1 A seventeen-year-old girl was threatened a t knife-point by a previously unknown assailant and cruelly raped. Despite the fact that they had spent a few hours together prior to the attack, she could not describe, under routine police questioning, either her assailant or the scene of the crime. However, under hypnosis, she was able to reconstruct a n identi-kit portrait of the suspect and guided the police to the scene of the crime where they recovered the knife which was used to threaten her. The identi-kit portrait was accurate enough to lead to the arrest of a suspect who later confessed to several similar rapes, including the cruel attack on the same young girl. Case No. 2 A restaurant manager was robbed by a n armed assailant, as he was returning home and parking his car. At gun-point he completely acquiesced to the demands of his assailant, handed over all his money, and allowed the assailant to dryve away immediately. Under routine police questioning, he was unable to recall any details of the event. When questioned under hypnosis, however, the victim was able to reconstruct a n identi-kit portrait of the robber, describe the robber's car. and give an exact time-table of the event. I t was later learned that the victim's father was a well-known war hero. The victim considered his behaviour under gun-point during the crime as being cowardly and not befitting the standards of behaviour expected of his father's son. His complete memory repression under routine interrogation could be related not only to the anxiety aroused by the threatening situation, but especially to the guilt feelings related to his "shameful" behaviour. At a later date, the robber was apprehended and it was found that the identi-kit was astonishingly accurate in detail. The car, however, did not fit the description by the victim.
b) Cases in which hypnosis was used in order to recall forgotten details or events that at the time of the crime seemed ordinary or insignificant (therefore, not worth remembering), but at a later date, when the crime was reported, became most crucial and evoked different levels of anxiety: Case No. 3 Two buses in Northern Israel were found to contain hidden bombs, one of which later exploded. When questioning the bus drivers, the police concentrated on having the drivers try to recall suspicious looking passengers carrying parcels. Due to the length of the two bus routes and the large number of passengers, it was impossible for the bus drivers, under routine questioning, to recall any significant details. However, one of the drivers was subjected to hypnosis and reconstructed the entire route, (revivication), and was thus able to report every small event and detail which took place. He reported that upon arriving at a certain bus stop a dark-skinned youth entered the bus carrying a parcel. When the driver handed him his change, he noticed a cold sweat on the young man's palm. Therefore, during hypnosis he pointed out the youth as being a likely suspect. Although the driver only faced the youth for the short period of time needed to sell him a ticket, he was able to reconstruct a n identikit portrait. At a later date, a suspect, whose description perfectly fitted the identi-kit portrait, was arrested and confessed to the crime. 78
c) Cases in which hypnosis was used when the subject seemed to re-call the actual information needed by the investigating team, but the information did not fit in with the other evidence obtained: Case No. 4
An Israeli soldier was reported missing from his base. The testimony given by two witnesses was contradictory. One of them stated that the soldier left the base in a certain vehicle travelling north. A second witness testified that he saw the missing soldier on the base after the same vehicle had allegedly left the base. I t was of crucial importance to the investigating team to determine the correct version in order to begin the search for the missing soldier. Both witnesses were questioned under hypnosis, the first retracted his original statement, saying that the soldier he saw in the vehicle was not the soldier in question, but one who resembled him. The second witness confirmed his original statement. The body of the missing soldier was later found near his base, a fact which corroborated the results of the questioning under hypnosis.
Results and Discussion Among the first forty cases involving the use of hypnosis twenty-four cases showed a significant improvement in memory recall. The increment of infonnation delivered through hypnosis was assessed in sixteen cases out of the twenty-four. The assessment was determined by the actual apprehension of the criminal involved or by additional independent evidence brought out in the course of the investigation. The information was found to be generally accurate in fourteen of the sixteen cases assessed. I n the other two cases, the information was contradictory to other evidence gathered under routine investigation. Therefore, in fourteen out of forty cases in which hypnosis was used to improve the memory of eye witnesses and/or complainants, a significant increase of accurate information was gained. According to the data gathered, it is believed that the information elicited by hypnotic techniques of memory improvement is generally reliable, but there is still a possibility of details being inaccurate or distorted. Therefore, this material should serve the criminal investigator or~lyas a guideline. The information recalled by the subject under hypnosis should always be corroborated with other evidence and facts established during the course of investigation. The information gathered under hypnosis should be considered as a working hypothesis, and not looked upon as being fact. There is always the possibility that the subject could have erred at the time of perception, or be influenced by his fantasies, wishful thinking, and memory distortion at the time of recall. I t was found that the increase in the amount of material recalled was a function of two main independent factors: the amount of anxiety evoked by the event itself, and the degree to which the material to be recalled is meaningful. More information was recalled in cases involving events evoking overwhelming anxiety which caused a motivated repression of memory. Less information was elicited in cases involving the recall of seemingly insignificant details at the time of the event which only became crucial afterwards. The data gathered indicate that the degree to which the material elicited is meaningful may have directly influenced the amount of information recalled in the hypnotic state. More information was recalled when the witnesses were asked to recall a sequence of events. Less information was recalled when the witnesses were asked to describe faces, persons, or places. The least amounl of information was recalled when the witnesses were asked to recall specific details such as licence plate numbers. Conditions for the Use of Hypnosis in Criminal Investigations It is suggested that hypnosis should be performed in criminal investigations only under the following conditions :-
1. When subjects who are witnesses or victims express their full willingness to cooperate. For obvious ethical considerations, and in order to protect their civil rights, hypnosis should not be used on suspects. The only exception to this rule could be the use of hypnosis a t the request of the suspect in order to help him to recall details which might provide a sound alibi. Again, this should be done only at the suspect's request and, preferably, in the presence of his attorney. 2. I n every case the subject's psychological welfare should be the primary concern of the operator. Preferably, pre-clinical evaluations should be carried out and counselling should be available. 3. The operator must be a trained psychiatrist or psychologist with additional specialized training in hypnotic techniques. 4. The operator should be unbiased and should concentrate his efforts only on using hypnosis to help the subject to recall the specific desired information. He should be aware that the subject could interpret the operator's intentions or pre-conceived notions, and this may lead to the distortion of the material elicited. It is obvious that under no circumstances should the operator refer to material which is not directly concerned with the predetermined goal of the interview. Conclusion The use of hypnosis was found to be a useful and effective tool for scientific interrogation in criminal investigations. It would appear that clinical techniques could be adapted in order to elicit information from people involved in police investigations. More rigorous study and simultaneous research on two levels is therefore recommended :Applied Research in Actual Investigations This is to be done by increasing the number of cases conducted, by training the investigation units as to which cases are suitable for hypnosis and how to utilize the results of hypnosis, and by carefully collecting all the relevant data in order to achieve more precise and refined findings. Methodological Research This experimentation in which fundamental problems will be tested has to be conducted, as far as possible in field situations, but has to deal with problems such as population and situation factors, time effects; problems which cannot be tested methodologically on the field application basis as employed here. Acknowledgement The authors wish to express their appreciation to M. Kaplan and I. Biran for their helpful assistance in the preparation of this work. References BARBER, T. X., and CALVERLEY, D. S., 1966, Toward a Theory of "Hypnotic" Behaviour. Experimental Analyses of Suggested Amnesia, J. Abn. Psychol, 17395-107. KROGER, W. S., 1963, Clinical and Experimental Hypnosis, Lippincolt. MITCHELL, M. B., 1932, Retroactive Inhibition and Hypnosis, J. Gen. Psychol., 7, 343-359. ROSENTHAL, B. G., 1944, Hypnotic Recall of Material Learned Under Anxiety and Non-Anxiety Producing Conditions, 3.Exp. Psychol., 34, 369-389. J. M., and RIDDLE,E. E., 1932, The Effect of Hypnosis on Long STALNAKER, Delayed Recall, 3.Gen Psychol, 6, 429-440. TRUE,R. M., 1949, Experimental Control in Hypnotic Age Regression States, Science, 110, 583-584.
(1977), 17, 77
The Use of Hypnosis in Police Investigation: A Preliminary Communication M. KLEINHAUZ, I. HOROWITZ and Y. TOBIN Headquarters Israel Police, Investigation Department, Criminal Identijcation Division, Jerusalem, Israel.
Hypnotic techniques were used in criminal investigations in order to improve the memory of forty subjects who were involved either as witnesses or complainants. The evaluation of the experience in these cases indicate that hypnos:'~may be a potential tool to elicit essential information from cooperative subjects. It was found that the amount of information elicited through hypnosis increased with the meaningfulness of the material to be recalled and the leuel of anxiety it involved. Some requisites for the use of hypnosis in police investigations are suggested. Introduction Although there is controversy concerning the theoretical foundation of hypnosis, there is much agreement among scientists concerning the ways in which the hypnotic state can be induced, and the changes in human behaviour as a result of hypnotic suggestion. For many years, hypnosis has been used by clinicians interested in facilitating their patients' recall of previously forgotten or suppressed material. Psychotherapists usually achieve hyperamnesia (memory recall greater than that achieved in a non-hypnotic state) using age regression, and revivication techniques. Age regression is when the subject is "brought back" in time and made to recall situations of his past life. With revivication the subject is made to relive, or re-experience, earlier events of his life, and all memories subsequent to the point to which he is regressed are erased. A review of the experimental literature dealing with memory recall under hypnosis shows that significant improvement occurred only for meaningful material. Stalnaker and Riddle (1932) reported a significant recall of prose and poetry learned at least one year earlier. Rosenthal (1944) found significant hypnotic hyperamnesia using poetry, and True (1949) reported improved recall when subjects were asked to recall the day of the week in which their birthday fell in the particular year to which they were given regression suggestion. However, Mitchell (1932), and Barber and Calverley (1966), found no improvemefit with hypnosis in the recall of nonsense material. Kroger (1963) adds another variable stating that it seems that whenever some emotional factor interferes with the recall of stored information, hypnosis will be an effectual tool to achieve hyperamnesia. Following a comparative study of recall in hypnosis, Rosenthal (1944) reported finding that in the absence of effective factors, hypnosis does not favour "recall of meaningless material, or of meaningful material which is not part of our organized context". On the other hand, he finds hypnotic hyperamnesia for some experiences of an emotionally disturbing nature and for contextual material. Case Reports The Scientific Interrogation Unit of the Israel Police began using hypnotic techniques in 1973. I t was found that much relevant information perceived at the scene of a crime was later forgotten, and eye witnesses and complainants were unable to report crucial facts and details. This forgotten material may
include descriptions of suspects, vehicles, licence numbers, weapons, etc. Hypnosis was used in order to enhance the memory of eye witnesses and/or complainants. Criminal investigations in which hypnosis has been used can be divided into three major categories :a) Cases in which it was assumed that the loss of memory was due to a motivated repression of details and/or events evoking overwhelming anxiety: Case No. 1 A seventeen-year-old girl was threatened a t knife-point by a previously unknown assailant and cruelly raped. Despite the fact that they had spent a few hours together prior to the attack, she could not describe, under routine police questioning, either her assailant or the scene of the crime. However, under hypnosis, she was able to reconstruct a n identi-kit portrait of the suspect and guided the police to the scene of the crime where they recovered the knife which was used to threaten her. The identi-kit portrait was accurate enough to lead to the arrest of a suspect who later confessed to several similar rapes, including the cruel attack on the same young girl. Case No. 2 A restaurant manager was robbed by a n armed assailant, as he was returning home and parking his car. At gun-point he completely acquiesced to the demands of his assailant, handed over all his money, and allowed the assailant to dryve away immediately. Under routine police questioning, he was unable to recall any details of the event. When questioned under hypnosis, however, the victim was able to reconstruct a n identi-kit portrait of the robber, describe the robber's car. and give an exact time-table of the event. I t was later learned that the victim's father was a well-known war hero. The victim considered his behaviour under gun-point during the crime as being cowardly and not befitting the standards of behaviour expected of his father's son. His complete memory repression under routine interrogation could be related not only to the anxiety aroused by the threatening situation, but especially to the guilt feelings related to his "shameful" behaviour. At a later date, the robber was apprehended and it was found that the identi-kit was astonishingly accurate in detail. The car, however, did not fit the description by the victim.
b) Cases in which hypnosis was used in order to recall forgotten details or events that at the time of the crime seemed ordinary or insignificant (therefore, not worth remembering), but at a later date, when the crime was reported, became most crucial and evoked different levels of anxiety: Case No. 3 Two buses in Northern Israel were found to contain hidden bombs, one of which later exploded. When questioning the bus drivers, the police concentrated on having the drivers try to recall suspicious looking passengers carrying parcels. Due to the length of the two bus routes and the large number of passengers, it was impossible for the bus drivers, under routine questioning, to recall any significant details. However, one of the drivers was subjected to hypnosis and reconstructed the entire route, (revivication), and was thus able to report every small event and detail which took place. He reported that upon arriving at a certain bus stop a dark-skinned youth entered the bus carrying a parcel. When the driver handed him his change, he noticed a cold sweat on the young man's palm. Therefore, during hypnosis he pointed out the youth as being a likely suspect. Although the driver only faced the youth for the short period of time needed to sell him a ticket, he was able to reconstruct a n identikit portrait. At a later date, a suspect, whose description perfectly fitted the identi-kit portrait, was arrested and confessed to the crime. 78
c) Cases in which hypnosis was used when the subject seemed to re-call the actual information needed by the investigating team, but the information did not fit in with the other evidence obtained: Case No. 4
An Israeli soldier was reported missing from his base. The testimony given by two witnesses was contradictory. One of them stated that the soldier left the base in a certain vehicle travelling north. A second witness testified that he saw the missing soldier on the base after the same vehicle had allegedly left the base. I t was of crucial importance to the investigating team to determine the correct version in order to begin the search for the missing soldier. Both witnesses were questioned under hypnosis, the first retracted his original statement, saying that the soldier he saw in the vehicle was not the soldier in question, but one who resembled him. The second witness confirmed his original statement. The body of the missing soldier was later found near his base, a fact which corroborated the results of the questioning under hypnosis.
Results and Discussion Among the first forty cases involving the use of hypnosis twenty-four cases showed a significant improvement in memory recall. The increment of infonnation delivered through hypnosis was assessed in sixteen cases out of the twenty-four. The assessment was determined by the actual apprehension of the criminal involved or by additional independent evidence brought out in the course of the investigation. The information was found to be generally accurate in fourteen of the sixteen cases assessed. I n the other two cases, the information was contradictory to other evidence gathered under routine investigation. Therefore, in fourteen out of forty cases in which hypnosis was used to improve the memory of eye witnesses and/or complainants, a significant increase of accurate information was gained. According to the data gathered, it is believed that the information elicited by hypnotic techniques of memory improvement is generally reliable, but there is still a possibility of details being inaccurate or distorted. Therefore, this material should serve the criminal investigator or~lyas a guideline. The information recalled by the subject under hypnosis should always be corroborated with other evidence and facts established during the course of investigation. The information gathered under hypnosis should be considered as a working hypothesis, and not looked upon as being fact. There is always the possibility that the subject could have erred at the time of perception, or be influenced by his fantasies, wishful thinking, and memory distortion at the time of recall. I t was found that the increase in the amount of material recalled was a function of two main independent factors: the amount of anxiety evoked by the event itself, and the degree to which the material to be recalled is meaningful. More information was recalled in cases involving events evoking overwhelming anxiety which caused a motivated repression of memory. Less information was elicited in cases involving the recall of seemingly insignificant details at the time of the event which only became crucial afterwards. The data gathered indicate that the degree to which the material elicited is meaningful may have directly influenced the amount of information recalled in the hypnotic state. More information was recalled when the witnesses were asked to recall a sequence of events. Less information was recalled when the witnesses were asked to describe faces, persons, or places. The least amounl of information was recalled when the witnesses were asked to recall specific details such as licence plate numbers. Conditions for the Use of Hypnosis in Criminal Investigations It is suggested that hypnosis should be performed in criminal investigations only under the following conditions :-
1. When subjects who are witnesses or victims express their full willingness to cooperate. For obvious ethical considerations, and in order to protect their civil rights, hypnosis should not be used on suspects. The only exception to this rule could be the use of hypnosis a t the request of the suspect in order to help him to recall details which might provide a sound alibi. Again, this should be done only at the suspect's request and, preferably, in the presence of his attorney. 2. I n every case the subject's psychological welfare should be the primary concern of the operator. Preferably, pre-clinical evaluations should be carried out and counselling should be available. 3. The operator must be a trained psychiatrist or psychologist with additional specialized training in hypnotic techniques. 4. The operator should be unbiased and should concentrate his efforts only on using hypnosis to help the subject to recall the specific desired information. He should be aware that the subject could interpret the operator's intentions or pre-conceived notions, and this may lead to the distortion of the material elicited. It is obvious that under no circumstances should the operator refer to material which is not directly concerned with the predetermined goal of the interview. Conclusion The use of hypnosis was found to be a useful and effective tool for scientific interrogation in criminal investigations. It would appear that clinical techniques could be adapted in order to elicit information from people involved in police investigations. More rigorous study and simultaneous research on two levels is therefore recommended :Applied Research in Actual Investigations This is to be done by increasing the number of cases conducted, by training the investigation units as to which cases are suitable for hypnosis and how to utilize the results of hypnosis, and by carefully collecting all the relevant data in order to achieve more precise and refined findings. Methodological Research This experimentation in which fundamental problems will be tested has to be conducted, as far as possible in field situations, but has to deal with problems such as population and situation factors, time effects; problems which cannot be tested methodologically on the field application basis as employed here. Acknowledgement The authors wish to express their appreciation to M. Kaplan and I. Biran for their helpful assistance in the preparation of this work. References BARBER, T. X., and CALVERLEY, D. S., 1966, Toward a Theory of "Hypnotic" Behaviour. Experimental Analyses of Suggested Amnesia, J. Abn. Psychol, 17395-107. KROGER, W. S., 1963, Clinical and Experimental Hypnosis, Lippincolt. MITCHELL, M. B., 1932, Retroactive Inhibition and Hypnosis, J. Gen. Psychol., 7, 343-359. ROSENTHAL, B. G., 1944, Hypnotic Recall of Material Learned Under Anxiety and Non-Anxiety Producing Conditions, 3.Exp. Psychol., 34, 369-389. J. M., and RIDDLE,E. E., 1932, The Effect of Hypnosis on Long STALNAKER, Delayed Recall, 3.Gen Psychol, 6, 429-440. TRUE,R. M., 1949, Experimental Control in Hypnotic Age Regression States, Science, 110, 583-584.
