olygraph tests have long been used as a method for detecting deception, and now a specialised technique is being used to determine whether a crime suspect has guilty knowledge related to the crime in question. The Concealed Information Test (CIT) uses a set of multiple-choice questions that refer to crime-specific details, such as the make and model of a car used in a drive-by homicide.
The test assumes that suspects with “guilty knowledge” will recognize the crime-relevant information and react more strongly to relevant items than to irrelevant items, while those without guilty knowledge will have no differential reactions. Research has found that the CIT has an accuracy rate of approximately 95%, with very low risk of misclassifying innocents as guilty.
The CIT is considered to be a standardised and highly accurate psychophysiological method for deception detection, and is widely accepted by the scientific community around the world. It is used for the evaluation of all types of suspects in both white-collar and criminal cases, and may be considered as scientific evidence in legal proceedings. It is crucial to ensure that the information used in the test is only known by the guilty party, and kept hidden from the media or third parties.
This technique is particularly useful when a child abduction case is revealed as a homicide investigation, and investigators need to narrow down multiple suspects. The CIT can be used to good effect in such cases.
In addition, the CIT is recommended for use when examining offenders with psychopathic traits, as the orienting response is likely to enhance their unusually low lability.
While the CIT has proven to be an effective tool in identifying guilty knowledge, it is important to note that polygraph tests are not 100% accurate and the results cannot be used as evidence in court. Nevertheless, the CIT is a valuable tool in helping investigators to focus their efforts and narrow down suspects, particularly in cases where there are many possible suspects.