Truth switching

Techniques > Interrogation > Truth switching

Description | Example | Discussion | See also

Description

Start with easy questions that they can comfortably answer truthfully. Then switch to questions where they will likely lie. Then keep switching back and forth.

When you switch, watch for a change in body language. Notice how their body language changes when they lie. Only when you know this, ask the key questions where you want to know if they are being truthful.

Try to keep the stress levels reasonably level in these questions. You may also want to try to find the difference between body language for stress and body language for lying.

Example

Do you like football? Do you think the team played well yesterday?...Are you a truthful person? If you found a bag in the street containing a lot of money, would you keep it? ... Do you like coffee? Do you like sugar in your coffee? ... Would you like a cup of coffee now? ... Where do you live? Were you there at 10pm on Thursday?

Discussion

When people lie, they typically change their non-verbal signals, such as touching their face or making slight speech errors. Poker players call these 'tells'. The problem is that the subject may already know 'standard' tells and be carefully covering them up.

If you can find their lying tells, then you will be much more able to detect lies.

Calibrating for stress body language takes more work but can be a very useful supporting activity, as people become stressed when lying and it is easy to confuse people who are lying with those who are just feeling stressed by the interrogation.