It's hot weather: polygraph examiners should be telling you to drink plenty of water in the hour before testing

 It's hot weather: polygraph examiners should be telling you to drink plenty of water in the hour before testing

Of all four medical tracings monitored during a polygraph exam, the one for moisture changes at the fingertips is the most critical. If dehydrated, there can not be the same reaction during lying as if properly hydrated for the testing.

An analogy is: a car can't get a speeding ticket if it is out of gas.

Some less-experienced examiners will simply ignore the lack of fingertip 'sweat' changes and just monitor the blood and breathing, greatly reducing accuracy.