Knowledge is power. Humanity has understood this principle since ancient times. And since ancient times, there has been a never-ending quest for distinguishing truths from lies. Is the person in front of us honest? Are they lying to protect themselves or somebody else? This matter is of particular importance for intelligence and law enforcement. Governments need to have confidence that the information they receive is accurate and that the people who are entrusted with this information have the integrity to treat it responsibly. Similarly, intelligence services need to rest assured that the information they gather through human intelligence (HUMINT) is true and accurate, and that their sources are not lying to them. In the same vein, law enforcement agencies need to verify that suspectsʻ statements are true to solve criminal cases.
As such, the benefits of discovering lies are obvious. Over time, the polygraph – more colloquially known as the “lie detector” and technically referred to as psychophysiological detection of deception (PDD) – has undergone many changes in technology and methodology, and it remains in use today. In the US alone, over 70,000 people undergo polygraph tests each year. [source]
1.0 Historic overview
While many other techniques of detecting deception were used at different times, the formal invention of the polygraph is credited to William Moulton Marston, a US attorney and psychologist. In 1915, he built a device that could measure variations in blood pressure as a stress response during interrogations. [source]
In 1921, John Larson created the first polygraph that was commercially viable. His device measured heart rate and respiratory patterns during questioning in addition to blood pressure, making it more reliable than previous machines. In 1925, Leonard Keeler added improvements to the design by incorporating ink pens that would mark physiological changes on paper and facilitate further analysis. His design was popular among US law enforcement agencies. [source]
In the 1990s, the polygraph became digital. Software programs allowed for a more accurate recording and analysis of results, reducing bottlenecks in recording and interpretation, and introducing simpler interfaces for examiners.
2.0 How exactly does it work?
Modern polygraphs measure key physiological parameters such as respiratory patterns, heart rate, blood pressure, and skin conductivity, all of which fluctuate due to stress, anxiety or arousal during questioning.
2.1 The Process
The polygraph testing process typically involves multiple steps: [source]
- Preparation: The subject is seated in a controlled environment where sensors are attached to their body.
- Baseline Questions: To establish a baseline for the subject’s physiological responses, the examiner asks a series of neutral questions. These help determine the person’s normal physiological state. All polygraph questions are designed to be answered with a “yes” or “no”.
- Relevant Questions: Afterwards, the examiner poses specific questions related to the matter under investigation. The polygraph records the physiological responses throughout this questioning phase. An example question used in counterintelligence (CI) polygraphs could be: “Did you knowingly participate in any foreign intelligence activities against the United States?” The same questions can be asked multiple times during a session to compare or clarify physiological responses.
- Analysis: Software analyzes the data and translates the physiological responses into visual interpretations. Examiners look for significant changes in the readings when relevant questions are asked compared to baseline responses.
The underlying theory is that deceptive answers trigger physiological responses associated with stress or anxiety such as increased heart rate or perspiration. By noticing variations in these patterns, examiners assess whether the answers of a subject are truthful. However, the accuracy of such results remains questionable due to individual differences and subjectivity of interpretation. [source, source]
2.2 Polygraph Operators
In the US, the American Polygraph Association (APA) establishes standards for the education of polygraphers and offers accreditations to institutions that provide the training. In the US, there are only 11 institutions that are accredited by APA to offer the 400-hour Basic Polygraph Examiner Course or more advanced courses. The training involves teaching the use of polygraph equipment to detect deception. [source, source]
Some of these schools are:
- National Polygraph Academy
- American International Institute of Polygraph
- Marston Polygraph Academy
- The Polygraph Institute LLC
- Academy for Scientific Investigative Training
2.3 Use Cases
There are multiple current applications for polygraphs. Some examples are:
- Law enforcement Investigations: Law enforcement agencies use polygraphs as investigative tools to assess the truthfulness of suspects or witnesses during questioning.
- Employment Screening: The Employee Polygraph Protection Act (EPPA) restricts the use of polygraphs, making it illegal for most employers. Certain government agencies and private sector employers utilize polygraphs for positions requiring a high-level security clearance, which constitutes an exception.
- Background Investigations: In many cases, individuals applying for security clearances such as Top Secret (TS) must go through polygraph tests to verify their claims made on security forms and ensure there are no risks posed by undisclosed issues.
- Research: Polygraphs may be used in psychological research to explore issues related to honesty and trust.
In terms of law enforcement, polygraphs are mainly used as investigative tools, however, their results are inadmissible in court. The impact of polygraph results on individuals is higher in the intelligence community (IC), where the tests are required to obtain and maintain a security clearance. This is usually performed every 5-10 years depending on the clearance and position. Failing the polygraph can lead to disqualification or job loss. [source]
3.0 A viable tool?
The remains an ongoing debate about the effectiveness of polygraphs and its ability to detect lies. That said, many law enforcement agencies and intelligence services across the globe continue using it.
3.1 Strengths
The biggest strength of the polygraph is its ability to provide insights into physiological data during questioning. Changes in these parameters can indicate stress responses and be an indication for deception. This can be particularly useful in enhancing investigations, identifying suspects, examining statements, and extracting confessions. The APA estimates current polygraph decision accuracy to be around 87%, although this number remains highly debated. [source, source]
In background investigations, polygraphs can highlight certain problematic areas of an individual, which disqualify them from obtaining a security clearance. The fact that some intelligence agencies such as the CIA or the NSA continue to employ and improve polygraph testing indicates that they believe in their effectiveness.
The whole process of going through the polygraph can act as a deterrent. Knowing that their physiological responses will be monitored may discourage individuals from lying in the first place. [source]
While one important purpose is to mitigate the risk of foreign infiltration within agencies, the use of polygraphs extends beyond that. It is key in supporting clandestine service (CS) activities, which include verifying the credibility of recruited agents and evaluating the accuracy of their intelligence to maintain operational integrity.
Moreover, intelligence agencies use polygraphs in debriefing defectors, walk-ins, and prisoners who may possess valuable information. Internally, polygraphs support investigations by helping to resolve allegations against employees. Further, they are used in regular re-investigations of staff to maintain their clearance. [source, source, source]
3.2 Weaknesses
The major downside of the polygraph is the possibility for false negatives and false positives. Physiological responses to the stress of questioning can be just that – stress. There is no unique physiological sign of deception. This is the reason why at the beginning of a polygraph test, an examiner asks the tested individual control questions to determine a physiological baseline. Other individual conditions can similarly affect the outcome and alter the interpretation. The overemphasis on the process of the polygraph may overshadow the actual results it produces. Indicators of stress do not necessarily prove a lie.
In 2003, the National Academy of Science concluded that: [source]
“Almost a century of research in scientific psychology and physiology provides little basis for the expectation that a polygraph test could have extremely high accuracy. The physiological responses measured by the polygraph are not uniquely related to deception.”
The research also highlighted the uncontrolled variation of emotional climate, selected questions and other factors that limit consistently accurate results.
It’s important to point out that the polygraph itself is just a tool. Like with other tools the skilsfulness of its user determines its effectiveness. Both the strength and weakness of polygraph results are heavily influenced by the professionalism, training, and years of experience of the polygraph operator. In the past, have been double agents, Aldrich Ames is one of them, who have successfully passed the polygraph despite supplying information to foreign governments. [source]
Individuals who are able to control their physiological responses better have a chance of passing despite being deceptive. Also, there are multiple medical and psychological conditions, such as anxiety or cardiovascular disorders that can negatively affect polygraph results.
Most developed legal systems do not admit polygraph results in court due to risk of misuse and lack of conclusive evidence for their accuracy. [source, source, source, source]
4.0 Future Outlook
As law enforcement and intelligence agencies increasingly seek reliable methods for assessing truthfulness, integrating new technology into polygraphy holds significant potential for enhancing its effectiveness. Continuing advancements in technology and the integration into polygraph systems of artificial intelligence (AI), machine learning, and new sensors promises to improve the quality of the results. AI, for instance, can identify correlations that may indicate deception while reducing the likelihood of false positives and negatives. [source]
The US Border Patrol uses AVATAR (Automated Virtual Agent for Truth Assessments in Real-Time) to screen immigrants at border entries. It is an AI system with an electronic interviewer where sensors track a person’s facial expression, voice, body language, and eyes for deception. The manufacturer claims an accuracy of over 80%. However, experts remain doubtful about its ability to detect lies and caution against an overreliance on such systems. [source, source, source]
Research and testing is done in other areas as well. For example, brain fingerprinting is a technique that detects concealed information by measuring brainwave activity, specifically through electroencephalography. Ocular-Motor Deception tests measure gaze position and pupil size with eye trackers to look for signs of deception. [source, source]
5.0 Conclusion
The polygraph has evolved from its rudimentary beginnings to become a complex tool utilized particularly in law enforcement and national security. However, polygraph results should be treated less as a hard fact but more as an indication that needs to be corroborated by other facts.
Polygraph testing remains common in the US, especially for security clearances within federal agencies, but its usage varies significantly worldwide. While polygraphs reveal stress indicators that may correlate with deception, it is not infallible. There is no definite physiological sign of deception and no scientific evidence that would confirm the effectiveness of polygraphs in accurately detecting deception. The potential for misinterpretation and the influence of external factors prevent it from being an ultimate “lie detector.”
Integrations with new technology such as AI promise to deliver significant improvements but their effectiveness remains to be seen.
