January 8, 2008, 12:35 PM ET

Take a Polygraph? Don't Do It, Roger

Asked on 60 Minutes whether he would take a polygraph test to support his denial of steroid use, Roger Clemens replied, “Yeah,” adding, “I don’t know whether they’re good or bad.”

Don’t do it, Roger. The polygraph is bad.

Based on measuring blood pressure and other physiological responses to neutral and provocative questions, it’s a voodoo device that can stain the innocent and exonerate the guilty. While projecting an aura of scientific certainty, the polygraph, or lie detector, has been repeatedly rejected by independent scientific reviews. Nevertheless, the FBI, various security agencies, and innumerable police forces regularly utilize the polygraph, though admissibility in court is severely restricted for lack of scientific evidence of reliability

With a little instruction, it’s said to be not difficult to beat the polygraph. Master spy Aldrich Ames, working deep inside the CIA, easily passed polygraph sessions in 1986 and 1991. (A Googling of “polygraph” turns up many instructional services for beating the machine.)

But that’s no impediment to survival of the polygraph. The best argument for the polygraph was offered by a wily pragmatist, Richard Nixon. Conferring in 1971 with fellow conspirators while trying to track down White House leaks, Nixon strongly urged polygraphing suspects, saying, “I don’t know anything about polygraphs, and I don’t know how accurate they are, but I know they’ll scare hell out of people.”

The scientific literature on the polygraph has been the subject of major reviews by the National Academy of Sciences, in 1983 and 2003, both giving the device failing marks. The more recent review concluded, “Its accuracy in distinguishing actual or potential security violators from innocent test takers is insufficient to justify reliance on its use in employee security screening in federal agencies.”

Various studies of the polygraph have noted its capacity for producing high numbers of false positives, i.e., flagging false responses where none actually exist.

Try carrying on with a government career with that mark on your record, unjustified though it may be.

Roger, don’t add to your many troubles by getting wired up to a polygraph. Given all the stuff they’re throwing at you, it can’t establish your innocence but it sure can deepen your woes.