Feature: Sgt. Mark Brennan – Why we need Evidence Based Policing

By Response Sergent Mark Brennan, Leicestershire Police

Evidence based policing is policing guided by scientific findings rather than individual opinion.

But what’s wrong with basing policing decisions on individual opinion? 

For some decisions, there is nothing wrong with this such as when we respond to a crime that has just happened.  Who is the victim? Who is the offender? Where is the threat?

The psychologist Daniel Kahneman called this using ‘system 1’ where we make instant, unconscious decisions.  Police officers are experts at taking these instant decisions and usually getting them right.

However Kahneman, in his book “Thinking, Fast and Slow” (2011) argued that there are other times where we need to utilise ‘system 2’ where we make slow, conscious effortful decisions to answer complex problems.

For an example of using ‘system 2’ try to answer this question without using a calculator:

16 x 23 =

As you can see using system 2 is hard work, which we sometimes don’t want to do or feel that we don’t have time to do.  Therefore some of you may have just tried a rough guess at the question or just decided it was too much work to even attempt!

The result being that you often end up with an incorrect answer or no answer at all.

The policing equivalents of the above maths question are:

  • How do we prevent a particular crime or anti-social behaviour problem?
  • How do we increase public confidence in the police in a particular group?
  • How do we motivate and engage our police colleagues and partners on a particular issue?

In the same way as answering the maths question, this will take a lot of hard work, which we sometimes don’t want to do or feel that we don’t have time to do.  Therefore we often just try a rough guess at the question or decide it was too much work to even attempt!  The result being that we often end up with an incorrect answer or no answer at all.

Kahneman identified a number of mistakes when we make these ‘rough guesses’ using ‘system 1’ when really the problem requires a slow, conscious ‘system 2’ decision making process.

In the attached video I talk about three of these common mistakes which are:

  • Failure to consider ‘regression to the mean’;
  • Failing to recognise that ‘correlation does not mean causation’; and
  • ‘Availability Biases’ influencing our understanding or how likely something is to happen.

All of these mistakes can be made by police professionals when they fail to take the time to apply ‘system 2’ thinking and instead rush to instant decisions using ‘system 1’ thinking.

By taking time to take a ‘system 2’ evidence based approach we can more often end up with the right answer to the big questions!

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