What is a polygraph test?
In general terms, a polygraph examination is a scientifically validated test used to determine the probability of a person answering truthfully or not to a set of predetermined questions. It is often referred to as a lie detector due to the context in which these examinations are generally implemented, however this is simply a term of convenience. The analytic theory of polygraph testing is that greater changes in physiological activity are loaded at different types of test stimuli as a function of deception and truth-telling in response to relevant target stimuli. [1]
The American Polygraph Association offers a more robust and comprehensive definition of a polygraph examination. It states as follows: “A psychophysiological test of deception or recognition sometimes referred to as lie-detection as a term of convenience. The polygraph examination is a standardized, evidence-based test of the margin of uncertainty or level of confidence surrounding a categorical conclusion of deception or the possession of knowledge or information regarding a test target issue. Test data are a combination of physiological proxies that have been shown to vary significantly with different types of test stimuli as a function of deception or truth-telling in response to the relevant investigation target stimuli. The psychological basis of responses to polygraph stimuli is thought to involve attention, cognition, emotion, and behavioural conditions. The examination consists of an interview phase, to clarify the issue under investigation and related test stimuli, a data acquisition phase, during which physiological responses to test stimuli are permanently recorded, and an analysis phase during which differences in responses to different types of test stimuli are numerically quantified to calculate a statistical classifier for a categorical test result. The examiner may also provide the examinee an opportunity to explain any physiological responses and resolve any remaining inconsistencies.” [2]
Polygraph examinations are a form of Physiological Detection of Deception (PDD testing) as defined by ASTM International Standard Terminology Relating to Forensic Psychophysiology. [3]
What are polygraph examinations used for?
Polygraph examinations can be used as a forensic tool in many various different circumstances and for various purposes. This may include as a forensic tool during investigations, for evidentiary purposes, as part of pre-employment vetting during recruitment processes, or as a data collection and mitigation tool used in continuous screening and risk management processes.
Polygraph Examinations Used in Investigations
During investigations, polygraph examinations are implemented as forensic tools to collect information and to assist in narrowing down the investigation by revealing potential suspects. A polygraph test is administered on persons who may have been involved in the matter under investigation, or who may have information regarding the particular matter. The test consists of a specialised interview to collect information and statements pertaining the matter, followed by the implementation of the examination itself, during which examinees are instructed to answer specific question designed to aid in the investigation. After the examination is completed, a report is compiled containing the information collected during the interview as well as the examination results. Investigators can use this information to aid in the investigation, which may include follow-up interviews, evidence collection, corroboration and investigation planning. If conducted properly, polygraph examination results may be submitted as part of a bundle of evidence in hearings and legal procedures.
Pre-Employment Polygraph Examinations
Pre-employment polygraph examinations are conducted on potential recruits to monitor for past behaviour indicating potential risk to the recruiting company. The company can elect at which point of the recruitment process the examination should be administered based on the company needs and existing vetting procedures. During a pre-employment polygraph examination, an applicant will be required to fill out a pre-designed form to collect information relevant to the company, the position and potential areas of risk. The applicant will then be interviewed by a qualified polygraph examiner using the form as a guideline, after which, the applicant will undergo the testing process with questions designed to monitor for potential risk to the company. The pre-employment polygraph process is an excellent tool to collect and compare information from applicants, gauge their integrity and to monitor for potential risk based on the past behaviour of the applicant. These examinations empower recruiters with the knowledge they need to make the best decisions for the future of their company. Used by law enforcement and defence agencies globally, pre-employment polygraph examinations are no longer a luxury, but a necessity in safeguarding your company and your employees.
Continuous Screening and Risk Management Processes
Polygraph examinations can be used as part of a risk management strategy to collect information from staff members and to monitor for potential risk. These examinations are conducted on a continuous basis throughout the year, usually in a pre-determined time frame. During the polygraph examination screening process examinees are interviewed by qualified polygraph examiners and afforded the opportunity to disclose any information relevant to the company, as well as any information which they feel may be beneficial for risk management process. Subsequent to the interview, examinees undergo the testing process designed to monitor for involvement in potential risk behaviour, such as stock theft, involvement with criminal syndicates or groups, leaking confidential information or other activities relevant to the particular company. These examination are utilized globally by law enforcement, security, defence agencies and companies associated with increased risk.
Are polygraph examinations legal in South Africa?
In short, yes. There is no legislation directly pertaining to polygraph examinations or any form of lie detection in South Africa. This means that polygraph examinations may be conducted provided that it is not done in a manner that infringes any existing laws. These laws include but are not limited to the Constitution of South Africa [3], he Labour Relations Act [5], the Basic Conditions of Employment Act (BCEA) [6], the Employment Equity Act [7] and the Criminal Procedures Act [8].
Unfortunately, this also means that there are no specific regulations in South Africa regarding the needed qualifications or standards of practice, and it is the responsibility of the clients and examinees to ensure that examinations are conducted in accordance with international standards of practice, using scientifically validated and reliable techniques, by qualified and accredited examiners and implemented in an ethical and fair manner. While there may not be any local regulations pertaining to polygraph examinations, international standards of practice are a requirement to ensure accurate and usable results, and if examinations are not conducted in adherence to these standards, it may lead to unusable results and the potential infringement of the rights of the examinee among various other potential detrimental consequences. [9]
Can a person be forced to undergo a polygraph examination?
There are various rights enshrined in the Constitution [4] that precludes a person from being forced to undergo a polygraph examination. Furthermore, polygraph examinations require the cooperation of the examinee, and as such, the voluntary cooperation of the examinee is both a matter of law and practicality. That being said, undergoing a polygraph examination may be part of a requirement for certain opportunities, and, supported by legal precedent, companies may include stipulations regarding polygraph examinations in employment contracts if it applied in a reasonable manner and subject to certain conditions. To use an analogy, a person can not be forced to work against their will, but an employer may employ a person to complete work subject to a contract and certain conditions. Similarly, a person may not be forced to undergo a polygraph examination and he or she may terminate the examination process at any time, however, this does not absolve the person from any potential repercussions if there were prior agreements, contractual obligations or other potential consequences.
On whose side is the examiner?
A polygraph examiner is an independent and neutral party whose function is to ensure that the examination is conducted ethically, fairly, and accurately, and who has the responsibility to compile and submit and accurate report.
Can nervousness affect the test results?
It is the norm for everyone to be nervous when they take a polygraph examination. As expected, the nervous state will increase a person's heart rate, blood pressure and elevate or heighten various physiological functions. This state is considered the person's normal pattern during and is not taken into consideration during the analysis of polygraph examination data as examiners identify and analyse specific sets of changes in the normal physiological pattern and within certain time-frames. It is part of the standard procedure for the examiner to take particular steps to reduce nervousness and anxiety, however it is important to note that there is no evidence that anxiety itself, high blood pressure, general nervousness or jitters can cause a truthful person to fail or a deceptive person to pass the polygraph test.
Can fatigue affect the test results?
Fatigue will not cause a person to pass or fail a polygraph test. Extreme fatigue may necessitate the rescheduling of an examination, but normal day-to-day weariness will not.
What does the polygraph record?
Modern day polygraph instruments records five or more channels of physiological data simultaneously. The components consist of two tubes placed around to the body on the stomach and chest to detect motion association with breathing and upper body muscle movements. Changes in skin moisture are monitored with sensors placed on the fingers or palms. Pulse and relative blood pressure are detected using a standard blood pressure cuff placed on the arm. Many instruments also record changes in blood vessel dilation using a finger sensor and all polygraphs now include sensors to detect body movement, usually in the form of a cushion called an electronic seat sensor. These components run continuously during the data collection phase of the polygraph examination to monitor for changes in physiological patterns during the examination. The examiner uses these components to monitor for a pattern of physiological responses that have been correlated to the act of being deceptive on a statistically significant level.
Does polygraph testing cause discomfort?
Historically, a fairly common complaint regarding polygraph examinations referred to discomfort caused by the blood pressure cuff placed on to the arm of an examinee. Modern polygraph instruments use much lower pressure and complaints regarding discomfort are extremely rare.
How long does a polygraph examination take?
Generally speaking a polygraph examination will take between one and two hours depending on the type of examination and the complexity of the issues being addressed. The majority of examinations will entail a standardized interview process as well as a data collection phase. Examinations taking less than an hour can occur, however irregularly short examinations are often associated with unvalidated or invalid procedures, and do not conform to international standards of practice.
Are voice stress devices a good alternative to the polygraph?
While purveyors of voice-based systems claim high accuracy, independent scientific studies have not supported those claims nor are scientists optimistic that these types of systems can ever be competitive in terms of validity or reliability, with some studies indicating that some of these systems may not even be able to record the very signal it purports to. Voice-based devices have a demonstrated capacity to elicit confessions from naïve examinees, but the scientific assessments of the validity of these systems have been universally disappointing. There are more than a dozen systems that have appeared since the 1970s, with most of them disappearing once the evidence for their poor performance becomes known.
References
[1] Nelson, R. 2016. Scientific (Analytic) Theory of Polygraph Testing. APA Magazine, 49(5).
[2] American Polygraph Association. (2024). Standards of Practice. Online: https://www.polygraph.org/docs/APA_STANDARDS_OF_PRACTICE_amended_23_August_2024.pdf
[3] ASTM International. (Reapproved 2017). Standard Terminology Relating to Forensic Psychophysiology. Designation: E2035
[4] The Constitution of the Republic of South Africa 108 of 1996. Online: https://www.gov.za/sites/default/files/images/a108-96.pdf
[5] Labour Relations Act 66 of 1995. Online: https://www.gov.za/documents/labour-relations-act
[6] Basic Conditions of Employment Act 75 of 1997. Online: https://www.gov.za/sites/default/files/gcis_document/201409/a75-97.pdf
[7] Employment Equity Act 55 of 1998. Online: https://www.gov.za/documents/employment-equity-act
[8] Criminal Procedure Act 51 of 1977. Online: https://justice.gov.za/legislation/acts/1977-051.pdf
[9] ASTM International. 2017. Standard Guide for PDD Examination Standards of Practice. Designation: ASTM E2062-11