How Long Before Lie Detector Evidence is Deemed Admissible in Criminal Trials?

In a recent police investigation concerning the possession of indecent images, Berkeley Sahota have become aware that Hertfordshire Police force are asking suspects to take part in polygraph tests.

Interestingly, the results of these "lie detector" tests help the police decide how thoroughly they should examine the computer equipment of a suspect. As a full forensic examination can take up to a year, the police are using these tests to help them to decide if and how they should allocate resources in these investigations.

It is important to note that as a well-known principle of criminal law, evidence from a lie detectors test is not admissible as evidence as proof of a crime in this jurisdiction.

Increasingly however, these lie detector tests are being used in other areas of the criminal justice system.

For example, convicted sex offenders are regularly tested once they are released on licence.

And in appeal cases, and occasionally when mitigating after a conviction, defendants will tell the court that they have volunteered to take a lie detector test. The results, they say, establish their innocence.

In our practice we have come across cases where our clients have expressed a wish to submit to a polygraph tests. We believe that the results can be useful when trying to persuade the Crown to review a decision to prosecute.

The jury is still out on whether the results of these tests will ever be allowed in evidence in a criminal trial in the UK. There would need to be a lengthy consultation and legislation to follow for this to become reality and in the United States, there is no consensus on the issue. While some states deem that polygraph tests should be allowed, others do not as polygraph tests are often criticised for their inaccuracy.

At present however, there seems little prospect of any change in our criminal procedure along these lines.