JONNY PHILLIPS (V/O): The lie detector, or polygraph. We've all seen the movies. Some steely eyed spy trying to conceal the truth from a mysterious interrogator. But can you beat a lie detector in real life?
Lying is a stressful business. The natural physiological reactions to telling a bit fat whopper is that your pulse quickens, you breathe faster and you start to sweat. Polygraphs work by detecting these changes. So any spike on the chart can indicate stress and therefore the possibility of a lie. So the key to deceiving a lie detector is to try and hide your real stress levels.
24 hours earlier I nicked Richard's games console. The question was, could I hide my act of dishonesty from the machine?
I was hooked up to it so that my breathing, skin conductivity and blood pressure could be measured.
Polygraph tests start with the examiner asking a series of basic questions to which the answers are known to be true. This establishes a baseline which indicates the average stress levels of that individual.
JONNY (PTC): Now one rumoured technique used by old spies was to put a drawing pin in their shoe. Now I'm gonna press my toes down onto this pin during the baseline questions. Hopefully the pain will increase my stress levels, so that during the potentially incriminating questions my nervous stress won't register any higher on the charts.
EXAMINER (SYNC - TO JONNY): OK. I'm gonna ask you a series of questions. I just need you to answer yes or no to each question.
Are you known as Jonny?
JONNY (SYNC - TO EXAMINER): Yes.
EXAMINER: Is today Tuesday?
EXAMINER: Just keep perfectly still for me.
JONNY (V/O): Which is quite difficult when your big toe's jammed down on a drawing pin.
EXAMINER: Are you wearing a grey jacket?
JONNY (V/O): With the baseline questions over, it was time for the main interrogation to begin.
JONNY (V/O): I was also hoping another trick might fool the machine. Stress makes you sweat more which increases your skin conductivity, putting tell tale spikes on the graph. So earlier I'd sprayed my fingers with anti perspirant to reduce the flow.
EXAMINER (SYNC): The test has started. Regarding the missing games console, do you intend to answer truthfully each question about that?
Prior to age 25 did you ever steal anything from a shop?
Famously, in the late 80s, CIA agent Aldridge Ames beat two polygraph tests while he was spying for the Russians by apparently just being super relaxed. Have my techniques worked with similar results?
EXAMINER: Prior to 2005 have you ever taken anything from a friend knowing you would not return it?
EXAMINER: Do you know where the missing games console is right now?
EXAMINER: Did you take the missing games console that Richard was using?
EXAMINER: Well Jonny, we've come to the end of your test and I'm afraid to tell you that you actually failed the test. There was one particular question, which was did you take the missing games console from the bench in the lab? And it shows a significant change in your breathing, in you galvanic sweat resistance and your blood pressure. Um you failed one question, so you failed the entire test.
JONNY (V/O): I'd made a fatal error. Apparently the pain induced stress caused by the drawing pin produced a totally different spike to that caused by nervous stress. And tests have shown that most anti perspirants actually increase skin conductivity.
I may not have beaten the lie detector, but a failed test isn't enough for a conviction in a UK court of law. Although it might help persuade a jury.