Lie detector (polygraph) test have historically been inadmissible in Court (so even if someone take one, a jury is not allowed to hear the results). This is primarily because there are doubts about their reliability.
On 20th November 2013 Shuan Wright, the Police and Crime Commissioner for South Yorkshire, announced that they will be used in limited circumstances.
When will they be used?
They will be offered to offenders and potential offenders on a ‘voluntary basis’. It will be used as ‘a risk assessment and investigative tool for known sex offenders … as part of probation or bail conditions‘.
How much will it cost?
According to the Guardian, Mr Wright will spend £35,000 on the equipment and sending two police officers to be trained on using it to Texas (it’s a hard life).
Is this legal?
ss29-31 Offender Management Act 2007 provides for polygraph tests to be used as part of determining licence conditions for someone who is released from prison.
This was upheld (during a pilot scheme) as being lawful (in the sense of not being a breach of Art 8 ECHR) by the High Court in the case of C v MoJ  EWHC 2671 (Admin)). It is probably not surprising as it was voluntary and the challenge doesn’t fit particularly well into Art 8.
If there was a situation where release from prison would be conditional on taking a polygraph test, then this would be a different matter (and the courts would probably not allow that).
As for bail conditions? Under s3 Bail Act 1976, the Court may impose ‘such requirements as appear to the court to be necessary to‘ prevent him committing any offence on bail. This would be wide enough to cover the imposition of a polygraph test, but it would then be made a mandatory requirement which would involve different considerations.
My gut reaction is that there is a very good chance that this would be unlawful (under Art 5 ECHR), but time may tell.
The press release from the Commissioner indicates that he thinks it will be used for pre-charge bail in cases such as child pornography offences where there are often long periods of time before a charging decision is made. Again, I imagine that this would be challenged and be found unlawful.
But no harm really done, even if they don’t work?
That’s the question. Wikipedia has a good overview of how polygraphs work and how reliable they are.
The problem is that if they are unreliable, then why use them? It may get some questions right, but there are Type 1 and Type 2 errors. It will mean that people are wrongly labelled a greater risk than they actually are, which will impact on their liberty. More significantly (for the Commissioner) is that people who ‘pass’ a polygraph when they shouldn’t may not be identified as the risk that they are.
Whilst it is said that it will just be one part of a tool to get an overall view, the risk (as I see it) is that these tests will be administered by two officers who have been picked as ‘specialists’ in this area and have been sent to America to be trained in this. In light of that, there is a real danger that they will place too much reliance on the results.
This may just be a gimmick, but if I was in South Yorkshire I would be unhappy about my crime Commissioner spending money on pseudo-science.
The blanket ban on polygraph testing did not just mean that prosecutors were barred from using tests that implicated defendants, but the accused could not use tests that appeared to clear them. Currently, there are plenty of people in prison who state that they are victims of a miscarriage of justice who have passed a polygraph test. If a crime Commissioner is allowed to use them, why can’t they?