There is no such thing as a lie detector, according to Prof. David Lykken. The American public is deceived in thinking that the polygraph is valid. "A Tremor in the Blood" is a careful, scholarly examination of various tests in common use to determine truthfulness -- and a catalog of the reasons that Professor Lykken believes they are not to be trusted.
Nearly 1 million Americans underwent polygraph tests in 1980. Livelihoods, reputations, and the difference between acquittal and conviction rested on the scribbles from a machine whose accuracy in detecting the guilty is, Professor Lykken suggests, almost on a par with the toss of the dice.
The polygraph is attached to subjects to measure physiological responses to the answers they give to certain questions.Polygraphers feel that there is a measurable response which everyone exhibits when lying.
Can blood pressure, palm sweating, and breathing rates really separate the liars from the truthful? Professor Lykken feels that they cannot. He convincingly argues that there are some liars, particularly hard-bitten criminals, who can prevaricate without sweating a drop. On the other hand, a mistaken accusation can upset an innocent subject, and the lie detector cannot distinguish between that and a guilty response.
Sometimes the test is regarded as the key piece of evidence. In Wisconsin in 1974 James Mendoza was convicted of first-degree murder, even though eyewitnesses and physical evidence supported his claim of self-defense. But Mendoza failed a polygraph test, and jurors believed the readout.
Human beings are presumed to be "lie detectors" in some sense. This is the reason for jury trials and court appearance of both criminal suspects and their accusers. But the book suggests that the polygraph has supplanted this cornerstone of the justice system.
Polygraph tests are also common outside the courts. The majority of lie detector tests are used by employers to screen current and prospective employees. When someone fails such a test, he or she may be denied employment, lose his job, or be effectively blacklisted from future employment because of bad references -- without the benefit of due process, the presentation of evidence against him, or conviction by a jury of peers.
"A Tremor in the Blood" raises many important questions. It is unfortunate that this warning about the polygraph's dangers to one and all is not written for one and all.Professor Lykken provides a comprehensive history of the polygraph, technical descriptions of tests, and tables of statistics to assess the tests' validity. The book is an impressive challenge to the polygraph phenomenon, but it remains for someone to articulate these arguments for the average reader -- and juror.