critical item

What Is a Critical Item?

A critical item (also called the key item or target item) is the specific item in a Concealed Information Test (CIT) or Peak of Tension (POT) test that is known to be connected to the matter under investigation. The critical item is presented among several similar but unrelated foil items. A guilty examinee who recognises the critical item is expected to produce a differential physiological response to it, while an innocent examinee who does not possess this knowledge responds similarly to all items.

Example

In a CIT investigating a theft of a specific item, the critical item might be the stolen object (e.g., "a gold watch") presented among foils (e.g., "a diamond ring," "a silver bracelet," "a pearl necklace," "an emerald pendant"). An examinee who committed the theft would recognise the gold watch as the stolen item and produce a stronger orienting response — measurable as increased electrodermal activity and other autonomic changes — to that item compared to the foils.

Requirements for Valid Critical Items

For the CIT to work properly, the critical item must meet several criteria: it must be known only to investigators and the perpetrator (not publicly disclosed), the foil items must be equally plausible to an innocent person, and the critical item must be sufficiently distinctive that a guilty person would reliably recognise it. Violations of these requirements — such as media disclosure of crime details — can invalidate the test by allowing innocent examinees to recognise the critical item.

Relationship to Scoring

Scoring in CIT formats evaluates whether the examinee's response to the critical item is significantly larger than their responses to the foils. Statistical methods such as the lognormal ratio quantify this differential. A significantly elevated response to the critical item indicates the examinee possesses concealed knowledge about the matter under investigation.