Our Science


The classic theory behind criminal decision making is called 'expected utility theory'. What it says basically is that thieves make rational decisions about what and when to steal. The main thing that would put them off would be the prospect of being caught and punished.

This theory has driven everything from sentencing policy to the adoption of crime prevention strategies such as the invisible marking of goods using ultraviolet markers.

The only slight problem is that it doesn't work, never has.

During the most severe economic recession since the 1930s crime has actually decreased overall rather than rising. This goes completely against the theory of the rational criminal who would be expected to have become more numerous, more determined and more violent as economic conditions declined.

Another example is invisible marking using ultraviolet. Until relatively recently police forces worldwide spent a great deal of money providing invisible property marking services. The theory was that criminals would know because of associated publicity that property in a certain area was being marked. That would put them off stealing in that area. It did, but only in conjunction with visible property marking. The evidence shows that items that have only been marked invisibly still got stolen and bought. Why? Because thieves are not psychic, they have no way of knowing unless there is also a visible mark that something is protected.

However the recent emergence of a new field of science, behavioural economics, has allowed a better understanding of how criminals make the decision whether or not to steal.
Behavioural economics, pioneered by Professor Daniel Kahneman and Amos Tversky said that people were not always rational in their decision making under uncertainty. There were evolutionary thinking biases that fundamentally affected that process. They developed an approach known as Prospect Theory.

This was explained by Nobel prize winner Kahneman and Tversky in their 1979 paper Prospect Theory: An Analysis of Decision under Risk. It says basically that people make decisions based on the potential value of loss or gains and that the assessment of risk is not simply based on the certainty of punishment. Instead it is based on their emotional reaction based on experience and expectations based on heuristics.