During our seminars participants ask many interesting questions about the psychology of lying and factors that affect lie detection. A common question relates to the effects of repeating a false statement. Specifically, if a person tells the same lie over and over could the individual eventually come to believe the lie? We all have observed suspects who, based on analysis of the evidence, are obviously guilty of the crime yet display minimal deceptive behavior symptoms when they deny involvement in the crime. Has the suspect convinced himself that he did not commit the crime?

To answer this question it is important first to define exactly what is meant by a lie. Within the science of detection of deception, a lie is a statement that the person knows is false and is designed to benefit the person making the statement. Consequently, not all untrue statements represent a lie. For example, I recently talked to my brother about an incident that occurred during a spring break we took more than 20 years ago. He was convinced the incident occurred during a trip to Albuquerque. I was equally certain that the event occurred twelve months later when we traveled to Tennessee. Obviously, one of our recollections is not factual, but that person cannot be considered as lying because neither of us is knowingly making a false statement nor are we receiving any personal benefit by making the statement. The reason this is important in answering our question is that, by detection of deception standards, if a person actually believes as true a statement which in fact is false, it is no longer a lie. With this in mind, the answer to the question posed above really relates to the effect repetition has on the integrity and clarity of a person's memory.

There is no question that repetition increases recall. We probably all memorized multiplication and addition tables through repetitive use of flash cards. It is also well documented that repetition is a significant factor in altering beliefs or attitudes, e.g., advertisements, propaganda, social values, etc. However, neither of these repetitive efforts describe the context of generating a knowingly false statement for personal benefit. To put this in proper context, consider that a boy was playing with matches and burned down his parents' home. The boy repeatedly lies to his parents, friends and the police about playing with matches or being responsible for the fire. Over time, could the boy's repeated lies cause him to believe that he did not start the fire?

The answer is closely tied to the emotional state experienced at the time of an event. I have used the following class exercise very effectively to illustrate this relationship. I request that students write down five memories from their first 10 years of life. This usually takes a while as the students reflect back over many years. I then have the students write down the emotion they experienced at the time of each event. This is very easy for them to do and they readily write down an emotional state associated with their memory. It is curious that most of the reported emotions are negative such as fear, embarrassment, shame, sorrow and guilt. Evidently, the joy a ten-year-old girl experiences during a birthday party is not burned nearly as deep in her memory as the fear she experienced when, that same year, she got lost in the woods on a camping trip.

Most casual memories do erode over time and may be susceptible to alteration through suggestion, repetition or false association. But when a memory is directly connected to an intense emotional state, it tends to be much more rigid and psychologically indelible. This describes the circumstances of most criminal acts. When the previously mention boy burned down his parents' home, in all likelihood, he experienced tremendous fear and guilt as a result of his actions. This intense emotional state will cement the negative memory in his brain. Regardless of the number of times he denies being responsible for starting the fire, if he experienced a significant emotional state when he started it, it is highly unlikely that he would come to believe that he did not start the fire.

This explanation introduces a new question. What if a person who commits a crime does not experience a significant emotional state at the time of the crime? One circumstance that may lead to this condition is a person who is so intoxicated or under the influence of drugs as to greatly inhibit their emotional arousal at the time of the crime. The most common cause for this, however, is that the nature of an incident or event was non-emotional. Consider a wife who states that her husband arrived home from work at 6:30 PM last Friday. Because there was no strong emotional state associated with the time he arrived home, her memory in this area is malleable and, therefore, could erode with time and repetition. Each time she tells someone that her husband arrived home at 6:30 PM, she is more and more convinced that he did arrive home at 6:30. The same cause can be cited for the earlier mentioned difference between the recollections my brother and I had about the spring break we took together. The disputed incident was not associated with any intense emotions.

What then accounts for the apparent lack of deceptive behavior symptoms exhibited from some suspects who have repeatedly lied about committing a crime? The behavior symptoms investigators associate with lying have little to do with a suspect's feeling of guilt or remorse. Rather, they relate to the fear of being caught lying and subsequently suffering the consequences of their crime. Each time a guilty suspect lies successfully and escapes the consequences of his act he is fortified in his belief that he will not be punished. In essence, he becomes more confident telling the lie and his fear of being detected lying decreases. The more confident a suspect is in his ability to evade detection, the fewer deceptive behavior symptoms he will exhibit when he lies.

The question posed at the outset of this article was whether or not a suspect who repeatedly lied about committing the crime could come to believe that he did not commit the crime. If the crime in question resulted in a significant emotional state the answer to this question is, in all probability, no. Repeating a statement that the person knows is not true does not change the liar's perception of reality, e.g., the person still knows that he is lying. What probably does occur is that the person becomes more convincing in telling the lie because of repeated success at not being caught lying.