From: jcs
A polygraph test, often used in criminal investigations and interrogations, aims to determine a suspect’s truthfulness regarding a crime [00:10:11]. Polygraphs are not a foolproof system and can potentially be beaten, but a heightened state of anxiety makes success considerably more challenging and unlikely [00:10:40].
Pre-Test Phase and Psychological Pressure
During the pre-test phase of a polygraph exam, specific psychological techniques are often employed by interrogators [00:10:29]. This can involve:
- Amplifying Anxiety: The interrogator may endeavor to amplify a suspect’s anxiety before the test, especially when guilt is almost conclusive, to make the polygraph more challenging to “beat” [00:07:21].
- Disguised Reassurance: Psychological pressure can be disguised as reassurance, where the interrogator claims the test will confirm the suspect’s innocence if they are truthful [00:10:29]. This is often used when the suspect’s guilt is nearly certain [00:10:39].
- Explaining Failure Conditions: The polygrapher will inform the suspect of ways they can “fail” the test [00:10:54]:
- Failure to follow instructions: Not sitting still or answering questions as instructed [00:10:58].
- Lying: Deliberately providing untruthful answers during the test [00:11:08]. The polygrapher may emphasize that taking the test if one is guilty would be “stupid” [00:11:14].
Question Types
A directed lie polygraph test typically utilizes three types of questions [00:18:17]:
- Known Truth Questions: These are simple questions with obvious answers, like “Are you sitting down?” or “Are you wearing shoes?” [00:18:20]. They serve to establish a baseline reading for truth-telling and to disconnect the examinee’s thought patterns between questions for more accurate readings [00:18:27].
- Control Questions: These questions are designed for the examinee to purposely lie, often phrased to elicit a “no” response to something universally common (e.g., “Before 2018, did you ever lose your temper with someone you cared about?“) [00:18:44].
- Relevant Questions: These questions directly relate to the crime under investigation, and the examinee is expected to answer truthfully [00:19:01].
A guilty subject is expected to show a much stronger reaction to the relevant questions than to the control questions, even if they are lying on both, due to the immediate threat posed by the relevant questions [00:19:07].
Establishing Understanding of “Disappearance”
Before administering relevant questions, the polygrapher may discuss with the suspect what constitutes “causing someone’s disappearance” to ensure clear understanding. This involves exploring various physical ways one could murder or kidnap someone, such as stabbing, shooting, hitting with a blunt object, strangulation, drowning, burning, or luring into a trap [00:14:06]. The interrogator wants to confirm the suspect understands that the question “Did you physically cause [person]‘s disappearance?” refers to these actions, not just emotional harm leading to them leaving [00:17:12].
Post-Test Evaluation
After the test, the polygrapher evaluates the results. If a suspect fails the test, they are informed of the polygraph results and are typically pressured to admit to the truth [00:23:32]. The polygrapher may comment on the suspect’s ability to lie during the control questions, noting significant reactions as an indicator of knowing when a lie is being told [00:20:17]. This is presented as an indicator that any lies on “significant stuff about your wife” would be “even 10 times more amplified” [00:20:51].
Case Example: Chris Watts Interrogation and Polygraph Test
In the interrogation of Chris Watts, the polygrapher amplified his anxiety before the test [00:07:21]. During the pre-test, the polygrapher confirmed his nervousness was normal [00:09:48] and reassured him that her training and validated testing methods would prove his innocence if he was truthful [00:10:09]. She explained the two ways to fail the test: not following instructions or lying [00:10:54]. The polygrapher specifically applies the psychological technique for maximal effect, being almost certain of Chris’s guilt [00:10:50].
She also explained the directed lie test, where Chris would purposely lie to control questions like “Before 2018 did you ever lose your temper with someone you cared about?” [00:19:19]. After the test, the polygrapher directly told Chris he was “not honest” and “did not pass the polygraph test” [00:23:32]. She noted his “significant reaction” when lying during the practice questions, interpreting it as an indicator of his body’s truthful response to lying [00:20:37].