A polygraph test is really just a psychophysiology exam. The polygraph measures changes in breathing rate using pneumographs or straps that record chest movements. Polygraphs will either have one of two circulatory system measures - either blood pressure will be measured as seen here or heart rate will be measured. Breathing, heart rate and blood pressure can all be altered consciously by the subject. However, the third measure or sweat or skin conductance to electricity measured by Galvanometers here cannot be consciously controlled.

UnderCalifornia law, apolygraphtest is not admissible incourtunless all parties agree toadmitit into evidence. Because of this, test results are not admissible as evidence in a jury trial. This is unless the prosecutor and the defense attorney agree to have the resultsadmitted.

Why do you think many states including California do not admit polygraphs into court proceedings?

Do you think polygraphs genuinely measure lying? Use the above information and search the internet to answer this question. Have fun learning about polygraphs!