Polygraph and Investigative Services

Hendricks Polygraph, Inc. 

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Confidential Research, Inc. 

What is polygraph? 

In scientific terms, a polygraph is utilized in the psychophysiological detection of deception. ​According to the American Polygraph Association ("APA"), the term " polygraph" literally means " many writings." The name refers to the manner in which selected physiological activities are simultaneously recorded. Polygraph examiners may use conventional instruments, sometimes referred to as analog instruments, or computerized instruments. It is also important to understand what a polygraph examination entails. A polygraph will collect physiological data from at least three systems in the body. 


Corrugated rubber tubes (or electronic sensors) placed over the examinee's chest and abdominal area will record respiratory activity. Two small metal plates or disposable adhesive electrodes, attached to the fingers, will record sweat gland activity. Some instruments also monitor other activity. For example, a finger plethysmograph, which monitors blood volume in the fingertip, or motion sensors, which monitor general movements that might interfere with test data, are often used. It is important to note that polygraph does not include the analysis of physiology associated with the voice. Instruments that claim to record voice stress are not polygraphs and have not been shown to work any better than chance (i.e., accuracy is similar to making a decision based on a coin toss). 



​Who uses polygraph? 

According to the APA, four sectors of society routinely utilize polygraphs, specifically

  1. Law enforcement agencies at the federal, state and local levels. 
  2. Legal community representatives from U.S. Attorney offices, public defender offices, defense attorneys, as well as parole and probation departments. 
  3. Other U.S. Government agencies such as: the Department of Defense, and agencies that compose the U.S. Intelligence Community (CIA, DIA, NSA, etc) 
  4. Private sector: companies and corporations under the restrictions of the Employee Polygraph Protection Act of 1988, as well as private citizens in matters not involving the legal or criminal justice system. 

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​​How accurate are polygraphs in detecting deception?

​The APA believes that scientific evidence supports the validity of polygraph examinations that are conducted and interpreted in compliance with documented and validated procedure. Thus, such examinations have great probative value and utility for a range of uses, including criminal investigations, offender management, and selection of applicants for positions requiring public trust. The APA Standards of Practice set some of the highest professional requirements for its members to ensure their polygraph services are valuable, reliable and promote ethically responsible practices.


Hendricks Polygraph Inc. abides by the APA Standards of Practice. For additional information, navigate to the APA's website: www.polygraph.org