THE PSYCHOLOGY OF CRIMEthat certain brain areas are more active when people lie than when they
tell the truth, most of this research has averaged brain activity across
groups of liars compared with groups of truth-tellers. Testing individual
criminals could be much trickier. What’s more, there’s no single “neural
signature” for lying: rather, the network of areas associated with lying
tends to reflect increased mental effort. This means a crafty criminal could
spoil their brain scan simply by performing mental arithmetic during the
comparison truth-condition, so as to conceal their extra effort while lying.
Finally, critics of research in this area have pointed out that being told
to lie about something as mundane as a playing card in your hand – a
popular test in this field – is hardly comparable to lying about a murder
so as to avoid a lifetime in prison, or, for that matter, telling the truth in
the knowledge that if you’re not believed, you could spend years behind
bars. Also, the studies have involved drug-free, healthy participants – who
knows if the results would be the same with drug-addled psychopaths?
False confessions
Ask most people if they’d ever consider making a false confession and
they’ll probably say the chances are remote. It’s perhaps for this reason that
psychologists have found that confessions exert a powerful influence on
the decision-making of juries, leading them to assume that the confessor
must be guilty. Unfortunately, false confessions are more common than
we like to think. The Innocence Project – an American organization that
works to exonerate the falsely accused using DNA evidence – reports that
of the more than 200 people who have so far been exonerated, about 25
percent made false confessions or self- incriminating statements.
Saul Kassin at Williams College has conducted countless studies
showing the power of confessions to sway juror judgement. In a 1997
study with Katherine Neumann, for example, he measured how much a
mock jury was swayed by a confession, compared with how much they
were swayed by an eyewitness identification or a character testimony.
The confession was by far the most influential. He’s also shown how a
confession can contaminate other forms of evidence. For example, on
being told that a suspect has confessed, witnesses become more confi-
dent in their own incriminating evidence. On the other hand, providers
of alibis who are told that the suspect has now confessed suddenly lose
faith in their own memory. “Well, if he’s confessed,” they seem to be
saying to themselves, “I must have made a mistake about what the time
was when I saw him.”