Polygraphs

[Moonhead]

I think this is the right place for this question.... Ok, so if the Police have Polygraphs, and use them for a certain amount of crime investigations... why not just use the Polygraph in all cases, like murder? Someone told me its because they're not very reliable, but if thats true, then why use them at all?

[AndyAvery]

Polygraphs are risky as they detect stress in a person. This can cause problems as people being questioned by the police may well be stressed and give a false positive reading. If someone has psychopathic tendancies, they may well not feel emotion in the same way and give a false negative reading. As for should we use them, probably not.

[Moonhead]

Thanks Andy... I understand what you mean about the stress of the interview etc... so why use them at all? If they're deemed not reliable enough for some cases, then how can they be deemed suitable for any case at all? Hmmm, this is what you get from watching too much Trisha... ;o)

[lisaj]

Not an answer, but related : I seem to recall reading about a new camera technology that was aimed at airport security. It could detect the minute changes in the blood capilliaries in your face when lying. It also had an accuracy rate if roughly 95% I think...

[samiad]

there is a new form of lie-dectection that reads micro-expressions and is supposed to be almost impossible to fool check http://www.bbc.co.uk/science/humanbody/humanface/e
xp_deceit3.shtml it has been used in the states to great effect.