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Taking the Mystery Out of the Polygraph Test

Featured Author:

Sergeant Betsy Brantner Smith

Law Enforcement Career Expert

Sergeant Betsy Brantner Smith is a 29-year veteran of a large Chicago suburban police department and has held positions in patrol, investigations, narcotics, juvenile, crime prevention, hostage negotiation and field training. As a sergeant, she supervised her department’s K-9 Unit, served as a field training sergeant, recruitment team sergeant, bike patrol coordinator, and supervisor of the Community Education/Crime Prevention Unit. As a patrol sergeant, Betsy served on the Elderly Services Team, the Crisis Intervention Team, and as a supervisory member of the Honor Guard.

Betsy served as a host and content expert for the Law Enforcement Television Network (LETN) from 1999 – 2003. A graduate of the Northwestern University Center for Public Safety’s School of Staff and Command, Betsy writes for numerous law enforcement and government publications and has been an instructor for the Calibre Press “Street Survival” seminar since 2003. She also manages and instructs for Dave Smith & Associates, a law enforcement training and consulting company based in Illinois and is featured in the Biography channel’s new reality show “Female Forces.” Together with her husband, Dave “JD Buck Savage” Smith, she trains law enforcement personnel throughout the United States and Canada.

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• Letting Go of Law Enforcement's Ancient Thinking
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A polygraph exam is often a “make or break” part of the police testing process, but it’s often difficult to prepare for and even understand. As Richard Nixon said “I don’t know anything about lie detectors other than they scare the hell out of people!” Polygraph testing is used far more in government pre-employment processes than in the private sector. In recognition of this, the APA Research Center at Michigan State University surveyed 699 police executives from some of the largest police agencies in the United States to determine the extent of, and conditions in which, polygraph testing is being used for pre-employment screening (this survey excluded federal agencies). The major results of the survey showed that of the respondents 62% had an active polygraph screening program, 31% did not and 7% had discontinued polygraph screening. Admittedly, polygraphy is not an exact science, but if it’s going to be a part of your next law enforcement employment process, take the time to learn the basics.

The polygraph, or “lie detector” is an instrument that measures and records physiological responses like breathing rate, pulse, blood pressure and perspiration. The underlying theory of the polygraph is that when people lie they get measurably nervous about lying. Its name stems from “poly” for the multiple sensors used and “graph” for a single strip of moving paper that records information, although most polygraph examiners now use computer images instead of analog instrumentation. A polygraph examiner is generally a highly trained interrogator as well as the technical operator of the devise and will use their experience in addition to the machine to detect your truthfulness.

One of the most intimidating parts of the polygraph exam is being attached to the sensors that will collect physiological data from at least three systems in the human body. After being attached to four to six sensors, your polygraph exam will likely start with a pre-test interview to gain some preliminary information which will later be used for control questions; this is called the “Control Question Test,” or CQT. Often, the examiner may ask you to deliberately lie several times to test your responses; this is a “Directed Lie Test,” the DLT. They may also ask “probable-lie” questions, such as “have you ever stolen anything?” (even the most honest person has “stolen” a pen from work or a candy bar from their little sister or some other “theft” that concerns them enough to show a stress response when answering).

Finally, they may use the “Guilty Knowledge Test,” GKT, a test that compares physiological responses to multiple-choice type questions about particular facts that only the examiner and you would know. The majority of American Psychological Association members surveyed think that the GKT is the most accurate of these tests and consider it “a promising forensic tool.” However, polygraph testing is still largely controversial in the U.S., so why do so many police agencies use it?

In the Michigan State survey the great majority of the agencies using polygraphs indicate that lie detectors reveal information that cannot be obtained by other selection methods. They also stated that polygraph testing makes it easier to establish background information, that it deters undesirable applicants, and that it is faster than other methods of selection. About half of the agencies using polygraph testing for sworn positions also use it for non-sworn employment, such as dispatchers, records clerks, and even secretarial personnel.

CIA operative-turned-spy Aldrich Ames, convicted in 1994 of spying for the Soviet Union, famously passed several lie detector tests by allegedly being told by his Soviet handler to "Get a good night’s sleep, and rest, and go into the test rested and relaxed. Be nice to the polygraph examiner, develop a rapport, and be cooperative and try to maintain your calm.” Often subjects are also told to try and control their breathing or artificially raise their heart rate during control questions (IE: thinking about a scary movie scene even while you are telling the truth), but the bottom line is this: tell the truth.

Come to your polygraph exam well-rested and well-fed, dress appropriately, and answer the questions truthfully to the best of your ability. Most police agencies don’t expect you have lead a perfect life, but they do expect you to be truthful. After all, law enforcement is profession of honor and integrity. Good luck.

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