Blue Line


February 12, 2013  By Corrie Sloot

by Kevin Byrnes

It’s very important to interview all victims, witnesses, suspects and accused involved in a case to determine what really happened and thereby decide what charges, if any, you will lay. A big part of this process is ensuring you are getting a full and truthful account of events.

To be a successful interviewer, it’s important to be able to detect when there is deception, sensitivity and missing information. To advance your investigation, it is essential that you receive accurate and complete information in your interviews.

A domestic violence investigation began with a woman coming to the station to report offences perpetrated by her son in law. I started by establishing a relationship of rapport and trust with her, getting to know a little about her, connecting and making her feel comfortable communicating with me. While doing this, I watched the way she spoke and made mental notes of her body language.


The witness said her son in law had beat her daughter and their kids and although he had not injured the children, he had broken his wife’s hand. She also reported that he had a marijuana grow room in the basement which her daughter had nothing to do with. As we got into the subject matter of her report about her son in law, I continued making observations and noted the story made sense and flowed well. I did not note any increased tension or stress during the substantive part of the interview. Based on the story and my observations, I assessed that she was being truthful and proceeded to the next stage of my investigation.

After conducting the required background investigation, I obtained a search warrant, seized the marijuana and arrested the suspect. I verified more of the information the witness provided at each stage of the investigation, becoming even more confident in the truthfulness of her story. As a result, I was reasonably confident I would also charge the suspect with the assault offences but it was still important for me to speak with him, get his side of the story and make my own observations of his behaviour.

After ensuring the suspect had been cautioned and told of his right to counsel, I established a rapport with him. He was very relaxed and comfortable with me, speaking openly and leaning back in his chair with open body language. He remained relaxed when speaking about the marijuana cultivation because he knew he was already caught for that.

His demeanour changed when I began asking him about the offences related to his wife and children. His responses became evasive and his bodily language closed up; he sat up, crossed his arms and legs and turned his face away from me. The only time he denied assaulting his wife he leaned to the side and picked lint off the carpet. These observations made me more confident in my conclusion and inspired me to press until I obtained admissions.

As mentioned above, the first step is to establish rapport and create an atmosphere where truth is of the utmost importance. Connecting with a subject on a personal level and gaining their trust makes them more likely to be honest and forthright. It’s also easier for them to remember details of what they are expected to tell you. A calm relaxed person is in a much better position to access their memory because it is more available to them when they are not stressed. The ‘fight or flight’ response during stress causes changes in the body, including a limiting of blood flow to the thinking part of the brain.

Another benefit to the rapport building stage is that it gives you a chance to observe the subject when they are at ease and talking about information which is not case related, allowing you to establish a baseline for the person’s behaviour you can use later.

There is no one sign a person displays or behaviour you can observe that is a proof positive they are withholding information or lying. The formula is to establish a baseline for the their behaviour and watch for changes. The changes in both language and non verbal signs appear as a result of stress, in most cases because the person is being deceptive or withholding information.

The observations will continue throughout the interview and you will watch for clusters of changes. Do not jump in after one such change and call the person out.

In my interview with the son in law, his evasive language was accompanied by several non verbal body language indicators. Other signs may include personal grooming, picking lint, scratching, changing arm or leg position, changes in eye contact, licking lips or hard swallowing, cracking knuckles and nervous cough or laugh. Watch for changes from the norm.

The most important principal is to be attentive when people are speaking with you and watch for some of these signs. As you learn them and become more comfortable with the process, it will become second nature.

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