‘how can you tell if someone is telling the truth?’

‘how can you tell if someone is telling the truth?’

I have delivered a number of courses recently where investigative interviewing is a major part. One of the first things we cover is the incorrect assumption that Investigative Interviewing is about getting a confession. This is a common misunderstanding! The interview is about gathering checkable information which is pertinent to the incident being investigated. This includes what they say happened and their alibi if that applies. In order to understand this we should explore a few things which may happen before and during the interview.


Imagine that you have made a mistake at work, perhaps you have broken the line managers favourite mug. You decide not to say anything and quickly tidy up the pieces. A short time later, the line manager calls you from her office and asks if you can speak to her for a couple of minutes. Your first thought is she knows you have broken her favourite mug.  So what do you tell her? ‘It was an accident’, ‘I will try and get another one if she can tell you where it came from’, or even ‘It was not me, I know nothing about a broken mug’. No matter what it is, you sort out what you are going to say, even before you are asked. You may also decide not to volunteer the demise of the mug unless she brings it up first. This is all normal, we do it in our private and work life.


Put yourself in the place of a person being interviewed. You will have been given an appointment, perhaps by letter. You will know the reason for the interview, what you are being investigated for. You will do the same as in the mug incident, although depending on the nature of the investigation you will probably spend longer thinking about what you are going to say. There are three simple options to talking.

  1. The first, tell the complete truth.
  2. Secondly, tell a complete pack of lies
  3. Three, tell a combination of lies and truth.

You may even run what you are going to say past your friend or a union representative or a lawyer or your co subject. It may sound right to you but what do others think of the version of events you wish to tell? As a result, you may alter the story again and again.


The difficulty the interviewer has is if the third option is chosen then it is not very easy for us to distinguish what is true and what is a lie.  If the story told by the subject sounds like it could have happened then it all may sound true. So what do we do?


Check The facts

No matter what the subject or the witness/victim says, we are going to check it all.  If you think about it, the more information we can gather then the likelihood is that we will have gathered a lot of information which we can check. Check against other witnesses, computer or telephone records, or even CCTV. The next thing then is that if we want to check everything, the more we gather the better. The key here is to gather the information in fine grain detail, the more the better. Of course, it has to be relevant to the investigation. If someone says they have been hit on the head by a co worker, which hand? How hard? What sound did it make? What did it feel like? What was said before, during and afterwards? That is just a start, we need much much more.


Hand in hand with this is the question ‘how can you tell if someone is telling the truth?. The simple answer is that it is not easy. Body language is an inexact science, if you are not trained you will make a mistake. One way is to ask them if they have told the truth but of course they may lie when they answer. So the best way is gather as much detail as you can from the interviewee. The more information you gather, the more you have which you can cross check. A note here, if you have not been on one of our courses, not every witness will report the exact same details of an incident even if they all saw the same thing. This is called confabulation and we will cover it on our courses!


It’s all in the details

Finally, if we are going to tell a series of lies to explain what happened, we will make up the major points of the story but will not think about the real fine details of it. Imagine a horse race where the fences are the details we make up to tell the story. We do not think we will need to tell about every blade of grass between the fences. As an interviewer, these details, the blades of grass are important. They are potentially checkable facts and therefore we can then tell if they are lies, confabulation or true. Hopefully then you can see that a confession should not be the focus of the interview. Obviously if you get one then that is fine. No matter what they say though, get detail, detail and more detail. Even if they confess we should check that out too. They may be lying to protect others.