Is it good news? The Pentagon has unveiled a new weapon for our troops in Iraq and Afghanistan that will save American lives. It is a portable lie detector: 

known by the acronym PCASS, for Preliminary Credibility Assessment Screening System, uses a commercial TDS Ranger hand-held personal digital assistant with three wires connected to sensors attached to the hand. An interpreter will ask a series of 20 or so questions in Persian, Arabic or Pashto: “Do you intend to answer my questions truthfully?” “Are the lights on in this room” “Are you a member of the Taliban?” The operator will punch in each answer and, after a delay of a minute or so for processing, the screen will display the results: “Green,” if it thinks the person has told the truth, “Red” for deception, and “Yellow” if it can’t decide.

“We’re not promising perfection — we’ve been very careful in that,” Donald Krapohl, special assistant to the director at the Defense Academy for Credibility Assessment, told MSNBC, which reports on the deployment of the device today.

It’s a good thing that the DoD is not promising “perfection.” That would be very hard to achieve, to say the least. Even non-portable lie-detector systems have a startlingly poor record of ferreting out deception. And these are almost always used in highly-controlled circumstances in which the psychological pressure on the individual being questioned is at its maximum.

The list of spies who have defeated the polygraph to penetrate U.S. intelligence is lengthy and includes Aldrich Ames, the Soviet mole in the CIA, Robert Hanssen, the Soviet mole in the FBI, and Ana Belen Montes, who toiled away in the Defense Intelligence Agency on behalf of Cuba for a decade-and-a-half, until her apprehension in 2001. The most recent case is that of Nada Nadim Prouty, the Lebanese woman arrested this winter, who moved from sensitive positions in the FBI to even more sensitive positions within the CIA despite a fictitious marriage and ties to the terrorist organization, Hizballah.

The idea that our troops can rely on primitive polygraphs to make snap decisions on the battlefield about whom to trust and whom to suspect is a formula for disaster. One of our most attractive and useful characteristics as a society is fascination with and love of technology. Sometimes, however, fascination and love turn into obsession. We seem to be in the grip of a clinical case of that disorder here.