The polygraph is a 2 billion dollar American industry running about 2.5 million tests a year, yet it detects no lie. Its rubber tubes, blood pressure cuff and finger plates record breathing, cardiovascular activity and skin conductance, the signs of fight or flight arousal. Examiners prime subjects with a rigged stim test card trick, then compare reactions to irrelevant, control and relevant questions, while Japan uses the concealed information test, which looks for involuntary recognition of withheld crime details. The device began with William Moulton Marston at Harvard around 1915, inspired by his wife Elizabeth Holloway Marston’s remark that her blood pressure rose when she was angry. Marston later appeared in 1938 Gillette razor ads and created Wonder Woman and her Lasso of Truth. John Augustus Larson in Berkeley added breathing in 1921, and Leonard Keeler added skin response, made it portable and sold it to the FBI.

A 2003 National Academy of Sciences review of about 80 studies found the research weak and warned against screening employees. In the 1998 case United States v. Scheffer the Supreme Court upheld a ban on polygraph evidence, likening its accuracy to a coin toss, and most of Europe, Canada and Israel reject it in criminal trials. Agencies keep it because frightened subjects confess. CIA officer Aldrich Ames passed twice while spying for the Soviets, Green River Killer Gary Ridgway passed in 1984, and Kansas widower Bill Wegerle failed two tests after his wife’s 1986 murder, living under suspicion until DNA in 2005 identified BTK killer Dennis Rader.

• How the stim test convinces subjects the machine is infallible before the real questions begin
• Specific countermeasures like biting the tongue or pressing a tack in a shoe during control questions
• The KGB’s simple advice to Ames: sleep well, be friendly and stay relaxed
• A 2013 federal crackdown involving about 30 agencies against people teaching how to beat the test
• The next generation of truth machines built on fMRI scans and AI analysis of micro-expressions