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Catching A Suspect In A Lie: Not Always A Symptom Of Guilt

May-June 2007 (click here for printable version)

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A skilled investigator learns to withhold certain inside information from a suspect during an interview in the hope that he can catch the suspect in a lie. For example, the suspect may lie about knowing the victim, being in the vicinity of the crime or having a prior conviction. This documented lie can later be used to good advantage during an interrogation where the investigator states that just as he knows the suspect lied about (knowing the victim) the investigator also knows that the suspect committed the crime. Furthermore, the documented lie can be used to impeach the suspect's credibility and character, e.g., "If you don't get this straightened out today no one is ever going to believe anything you have to say in the future. People are going to say, eWe know Fred lied about knowing her, Fred is probably also lying when he says that he is sorry he did this.'"

 

The attack on the suspect's character does not end during the interrogation. At trial the prosecutor may call the investigator to the stand to testify that during the investigation the defendant lied about knowing the victim. The jury, of course, is led to believe that if the defendant lied to the police about knowing the victim that the only possible logical conclusion is that he is also lying when he denies killing the victim. One need not possess a degree in philosophy to recognize the fallacy of this argument n If Johnny comes home from school and lies about the grade he received on a recent algebra test that lie does not increase the probability that Johnny is also the student who pulled the fire alarm at school last week.

 

Nonetheless, it is true that guilty suspects do lie during the course of an investigation and there are many documented cases where the person guilty of a crime was identified primarily because he was caught telling a minor lie. Offsetting these cases, of course, are those where innocent suspects have also lied to the investigator. This web tip will offer guidelines to help the investigator determine how much weight to place on the fact that a suspect has been caught in a lie.

 

Evaluate the Suspect's Level of Motivation to Tell The Truth

 

Consider two suspects, Tom and Jerry, who are both on probation for selling narcotics. A liquor store is robbed and Tom is seen standing in an alley two blocks from the store. The investigator asks him general questions about who he is, what he is doing in the ally and where he was ten minutes ago. The investigator then asks Tom, "Are you currently on probation?" Tom lies and says he is not.

 

Jerry was also picked up for the same robbery about two blocks from the liquor store but he was taken to the police station for a formal interview. The investigator has identified that the purpose for the interview is to determine whether Jerry was the person who robbed the liquor store. The interview questions all specifically relate to the liquor store robbery. The investigator then asks, "Are you currently on probation?" and Jerry says he is not.

 

Both of these suspect have lied about exactly the same thing. However, based strictly on that lie, factual analysis would predict that Jerry is much more likely guilty of the robbery than Tom. The reason for this is that Tom was operating from a much lower level of motivation when he lied about being on probation. His interview was informal and no clear purpose was stated for the interview; the questions were all general in nature. Tom had very little motivation to tell the truth about being on probation. In his mind he may well have figured that the questioning was routine and that his life would certainly not be negatively affected by the lie.

 

On the other hand, Jerry's interview was directed specifically toward the robbery and was conducted in a controlled environment. An innocent suspect operating from a high level of motivation approaches the interview with an expectation to tell the truth n not only about the issue under investigation but about peripheral issues as well. This is so even when the truth may reveal possible motives, access or opportunity. With the heightened level of motivation associated with Jerry's interview, he almost certainly would have told the truth about being on probation if he was innocent of the robbery. The fact that he chose to lie about his prior conviction becomes a strong factor pointing to his probable involvement in the robbery.

 

Evaluate the significance of the lie relative to the issue under investigation

 

A woman was raped and murdered in her apartment between 8:00 PM and 10:00 PM. One of the tenants within the apartment told the investigator that the night of the murder he was inside his apartment from 7:30 PM until the next morning. However, a neighbor saw the tenant leave his apartment at 9:00 PM and not return until after 10:00 PM. A second tenant told the investigator that he was working late and did not arrive at his apartment until after 10:00. In addition, he denied ever talking to the victim or knowing who she was. A friend of the victim, however, reported that the second tenant had asked the victim out for a date on a couple of occasions and she turned him down both times.

 

Both suspects have lied during their interviews. Based strictly on the nature of their lies, factual analysis would predict that the second suspect is more likely guilty of the murder. While lying about an alibi can be significant, innocent suspects may lie about an alibi to prevent the investigator from learning about other illegal or embarrassing activity (selling drugs in the park across the street, having an affair with a co-worker.)

 

Considering that this homicide was sexually motivated, lying about a prior relationship with the victim is a much more significant lie. If the second suspect was innocent, why not reveal to the investigator the fact that he knew the victim and asked her out for a date? Applying this principle, the following examples contrast two possible lies a suspect could tell during an interview. The second listed lie is closer to the issue under investigation and, therefore, a better indicator of the suspect's guilt.

 

Lying about owning a handgun vs. lying about firing a handgun the night of the murder

Lying about having an argument with the victim vs. lying about how the suspect injured his hand

Lying about having financial difficulties vs. lying about where suspect got the money to pay back rent

 

Evaluate the Reason for the Lie

 

Bob and Jeff are both interviewed as suspects in an investigation involving damage to a company van. Surveillance video shows both of them driving the van on the day it was damaged. During their interviews they both deny driving the vehicle on the day the damage occurred. When confronted with his lie, Bob explains that he lied because he used the company van to move some furniture to a new apartment. However, when Jeff is confronted with the surveillance video he does not give a tangible reason for lying other than to say that he simply forgot driving the van that day. Based only on this information, the probability is that Jeff is more likely than Bob to have caused the damage to the van.

 

When an innocent suspect is asked a question that would almost certainly lead to adverse consequences he may choose to lie to the question especially if the consequences to the secondary issue (unauthorized used of a company vehicle) are of similar or equal seriousness to the issue under investigation. When the reason for telling a lie involves significant consequences such as revealing illegal immigration status, having an outstanding warrant, exposing infidelity or a falsified resume this may simply be the innocent suspect avoiding consequences unrelated to the issue under investigation.

Jeff could make up a story in an attempt to explain away the surveillance evidence but that would involve telling another lie and further risking the investigator learning the truth. When confronted with this situation guilty suspects often blame poor memory bolstered by excuses such as being overworked, busy with something else or distracted by outside concerns.

 

Lies of Commission vs. Lies of Omission

 

A fire is started in a business and the nature of the fire suggests anger or revenge. The same week the fire was started Bill and Ted were both terminated from the business for violating company policy. The two employees are brought in for a formal interview concerning the arson. The investigation indicates that Ted is disgruntled because he was denied a promotion. A criminal record check reveals that Bill has a prior conviction for battery.

 

During a formal interview Bill and Ted both deny starting the fire or knowing anything about the fire. When asked about his feelings toward the company, Bill never volunteered any information about being disgruntled or being turned down for a promotion. Consequently, Bill has "lied" through omission. On the other hand, Ted is specifically asked whether or not he has appeared in court on any matter. Ted lies through commission and says he has not. Based only on these two lies, Ted is more likely guilty of starting the fire than Bill.

 

It requires much more confidence for a person to not only tell the truth but, further, to volunteer the truth when doing so places the suspect in a negative light. Lies of omission are commonplace in social situations and should not be considered strong evidence of guilt when interviewing a criminal suspect. It is precisely because of this that when a suspect volunteers incriminating information concerning motive, opportunity or access that the behavior is considered more typical of a truthful person.

 

In conclusion, it is an effective strategy to invite suspects to lie to the investigator during an interview. For example, if the investigator knows that the suspect was given the alarm code to the security system he should not ask, "I understand that you have the alarm code. When is the last time you used it?" Rather, he should invite the suspect to lie by asking, "Have you ever been given the alarm code?" Innocent suspects usually volunteer the truth, even if the truth reveals possible motives, access or propensity. Conversely, guilty suspects may lie to these types of questions. That is the general rule but, as this web tip points out, there are certainly occasions where innocent suspects will lie to the investigator.

 

When the investigator catches a suspect in a lie, the following rules are suggested for interpreting the lie with respect to the suspect's probable involvement in the issue under investigation:

 

(1) Lies told in an informal, low motivational setting are not as significant as lies told during a formal interview where the suspect is operating from a high level of motivation.

 

(2) The more related the lie is to the commission of the crime, the more likely the suspect is guilty. e.g., Lying about firing a weapon on the night of the shooting vs. lying about possessing a weapon of the same caliber used in the shooting.

 

(3) When confronted with the lie an innocent suspect usually has a reasonable explanation for lying, the guilty suspect may not.

 

(4) Lies of commission are more significant than lies of omission.



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