Occasionally, we are contacted by individuals who want to take a test because they cannot remember something, perhaps due to time lapse or memory impairment, and they hope taking a test will provide some clarity. Unfortunately for these individuals the polygraph cannot help.
The polygraph is not scouring the dark depths of a person’s mind to retrieve memories they cannot actively recall. The polygraph is simply collecting physiological data from the examinee via components attached to them. Analysis of this data allows the Polygraph examiner to make a judgement regarding the truthfulness of the examinee in relation to the questions asked during the test. The polygraph effectively allows the examiner to verify if the examinee is being truthful when they answer the question. A person cannot be truthful to the questions about the incident under investigation if they do not remember. Therefore, the examinee should only be asked questions to which they are certain they are telling the truth.
Asking questions regarding occasions when the examinee was under the influence of alcohol or illegal drugs can be problematic for polygraph testing. If the examinee suffered an alcohol or drug related blackout when they were intoxicated, this results in a gap in their memories. This is because being under the influence has interrupted memory consolidation and has resulted in a temporary block in the transfer of memories to the long-term storage part of their brain. Fundamentally the rapid increase in alcohol or drug levels has caused memory impairment or amnesia. An alcohol or drug related black-out does not mean that the person actually passed out or was unconscious, in fact the person may have been walking and talking and interacting with other people – but they haven’t actually formed memories of what they were doing.
While such amnesia may be severe in that it covers a number of missing hours, as the memories did not form they cannot be recovered, almost as if they never occurred at all. Sometimes fragments of the memory survive the black-out but these tends to be patchy and disjointed. In either of these circumstances a polygraph test should not be conducted concerning events which occurred during this amnesia as it is unlikely the person can be certain of what actually happened ultimately leading to a deception indicated result.
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