Forensic Psychology For Dummies (44 page)

Voice stress analysis faces lots of problems (hence the controversy). You know yourself that the pitch of your voice changes if you have a cold, or at different times of day. And, women generally have higher pitched voices than men, as well as pitch changing with age. As yet, I haven’t been able to get any answers to how voice stress analysis deals with these matters.

I once asked a voice stress analysis salesman for the research results of the product and in return received a load of abuse down the phone. I didn’t need his voice stress analysis equipment to tell me how angry he was with me for thinking that his product was less effective than he was claiming!

My concern is that voice stress analysis can be used by inexperienced and untrained call handlers, who simply watch the indicator on their screen (that’s supposedly indicating whether a person is telling the truth or not) instead of the call handler listening carefully to what the customer’s saying and how plausible they sound. In other words, does the use of voice stress analysis distract from the less hi-tech approach of carefully challenging what the person is claiming?

Truth drugs

Administering
truth drugs
(making the subject under questioning less wary in his replies because he’s in a highly relaxed state, induced by special drugs) to detect lying and deceit was popular for a short while in the second-half of the 20th century. The favoured drugs were sodium amytal or sodium pentothal, which are essentially sedatives. However, the reliability of truth drugs is questionable as a person in a dreamlike state is just as likely to be fantasising as telling the truth.

Under international law, using truth drugs to detect lying is regarded as a form of torture. Judges forbid evidence gained from using truth drugs.

Brain ‘fingerprinting’

Scientists are now able to produce a map of the electrical and related activity in the different parts of the brain, which commercial companies call
brain fingerprinting
. Mapping electrical activity in the brain is a more sophisticated lie-detection procedure than those I’ve already talked about (see the earlier sections ‘The polygraph’ and ‘Voice stress analysis’). Brain fingerprinting consists of putting a number of electrical detectors on a suspect’s head and mapping the pattern of electrical activity across the brain while the person is answering questions during a crime investigation.

The technique of brain fingerprinting is similar to the guilty knowledge procedure used with polygraph testing, except that this time the person being interviewed is shown pictures relevant to the crime mixed up with unrelated images, with the technique picking up on the images the suspect is particularly sensitive to.

Brain fingerprinting doesn’t require the suspect to speak. The procedure is claimed to work without the person needing to make a verbal statement, in which he may be lying or telling the truth.

There’s a lot of scepticism about using brain fingerprinting as a way of determining guilt or innocence. Some experts believe that commercial organisations are being misleading by naming it ‘fingerprinting’, using the term as a way of claiming similarities to the different and accurate fingerprinting procedure used in criminal investigations.

Yet, growing evidence suggests that, under carefully controlled conditions, brain-mapping has a part to play in determining a suspect’s innocence or guilt because of the suspect’s trust or faith in the procedure which as a result can produce a confession. Brain-mapping is an advanced version of physiological testing and is likely to be used more and more as the equipment becomes cheaper and less cumbersome.

Observing carefully: Behavioural approaches

You can find out a lot about what a person’s thinking and saying from the way they’re behaving. In the game of poker, where you have to decide whether another player is bluffing or has a great hand, such non-verbal clues are called a ‘tell’ (such as, a person shuffling their legs or scratching their ear showing that they’re lying). Using these clues to detect deception is fraught with difficulties. Studies show that looking at the way a person is behaving, and what he’s saying, as a means of determining whether he’s lying is more complicated than it first appears.

Non-verbal leakage (body language)

You can’t help thinking the term
non-verbal leakage
sounds a bit rude (conjuring up the image of a young child squirming because of needing the toilet but denying it furiously – although come to think of it the squirming
is
a form of non-verbal leakage and if correctly understood can indeed stop other forms of leakage!). The idea is that people show you what they’re feeling from the way that they behave, but they are not doing this consciously – as when a person threatens you by waving his fist in your face – they are doing it inadvertently. It’s unconsciously ‘leaking’ from them.

This non-verbal leakage is an aspect of
body language.
You express many things without the use of words, sometimes deliberately: a shrug of the shoulders, looking away, glaring into someone’s eyes. There are claims that some aspects of this non-verbal communication can be used to indicate lying.

Using body language to determine lying is unreliable in that everyone has their own way of behaving when telling a lie and that behaviour can change from situation to situation. Even poker players are aware that not every player has the same ‘tell’; you have to watch a person playing over time to spot if the ‘tell’ is special to that individual.