Wednesday, September 3, 2014

The Third Degree

In his 1955 book The Trouble with Cops, journalist Albert Deutsch discussed how detectives forced confessions from suspects. The Third Degree style of interrogation was not pretty, but became a staple of hard-boiled detective stories. “Good police work doesn’t need brutality,” Deutsch said, “It dehumanizes the police as well as the victim.” When the polygraph came into vogue in 1921, people viewed it as a way to get at the truth without anyone getting hurt. But is the polygraph a lie detector? Short answer: No!

In late 19th century, early criminologists talked about the physiological correlates of lying. Then in 1915, Dr. William Marston, working at Harvard’s psychology laboratory (started by Dr. William James), “discovered” the Systolic Blood Pressure Deception Test. The test measured a person’s blood pressure during an interview using neutral or emotionally charged words. The results could be read off an instrument. The Mütter Museum has some early examples of devices that measure continuous physiology, for example, arterial and venous pulses, as in the photo below.

The MacKenzie Polygraph (British, 1906-1910) from the Mütter Museum. Photo by George Grigonis.

Dr. Marston’s idea failed to make its way into the courtroom when lawyers for a murder defendant tried to use the deception test to prove the defendant confessed falsely. Thus, in the 1923 Frye v. U.S. decision by the U.S. Circuit Court in Washington, DC, a test such as a polygraph cannot be used as evidence until it has general acceptance within the science community. Dr. John Larson, a pioneer in using the polygraph in police work lamented to Deutsch: “The lie detector, as used in many places, is nothing more than a psychological third degree aimed at extorting confessions as the old beatings were. At times I’m sorry I ever had any part in its development.” The photo of the author portrays the stress of the subject under investigation. Since interrogations are inherently stressful, all bets are off as to the reliability of what a suspect says. In other applications—vetting employment applicants or exposing cheating spouses - the polygraph industry has thrived.

The author being grilled, with the help of a device for recording jugular vein and radial artery pulses. Photo by Evi Numen, props from the Mütter Museum by George Grigonis, detective played by Yan Xuan, M.D.

Fast forward to the present. The locus of lie detection migrates from the periphery to the brain. Real-time functional MRI imaging goes commercial, claiming “the first and only direct measure of truth verification and lie detection in human history!” (source: Businesses such as No Lie MRI are helping to settle disputes and aid security clearances, just as the polygraph has done, but this time touted as the equivalent of DNA matching. For the most part, criminal courts aren’t buying it. The problem is prejudicing juries. Because “seeing is believing,” jurors may give undue weight to pictures and not enough to nongraphic evidence. Some research on jurors’ behavior gives them more credit, but admissible tests must be nearly infallible.

Besides commercial applications, scientists are reluctant to endorse machine-aided truth finding. Courts say the technology is not ready to usurp the functions of judges and juries. The other issue is whether the use of neuroimaging or polygraphy is just as coercive as the proverbial rubber hose in the third-degree interrogation. The detective will say, “The test shows that you’re lying. Now come clean!” This may sound coercive, but it is legal. Many suspects, some mentally ill or intellectually disabled and unable to resist the bluff, will confess falsely or give up their right against self-incrimination. If you don’t believe it, check out The Innocence Project at They say about 25% of DNA-proven overturned convictions were of suspects who confessed falsely.

My unsolicited advice: Keep your nose clean; or, at least, when you’re caught, don’t tryto prove your innocence through a polygraph.