Background We examined the hypothesis that liars will report their activities strategically and will, if possible, avoid mentioning details that can be verified by the investigator. Method A total of 38 participants wrote a statement in which they told the truth or lied about their activities during a recent 30‐minute period. Two coders counted the frequency of occurrence of details that can be verified and that cannot be verified. Results Liars, compared with truth tellers, included fewer details that can be verified and an equal number of details that cannot be verified in their statement, and the ratio between verifiable and unverifiable details was smaller in liars compared with truth tellers. High percentages of truth tellers and liars were classified correctly based on the frequency counting of verifiable details (79%) or the ratio between verifiable and unverifiable details (71%). Those percentages were higher than the percentage that could be classified correctly (63%) based on verifiable and unverifiable detail combined. We compared our verifiability approach with other theoretical approaches as to why differences in detail between truth tellers and liars emerge.

According to the verifiability approach, liars tend to provide details that cannot be checked by the investigator and awareness of this increases the investigator's ability to detect lies. In the present experiment, we replicated previous findings in a more realistic paradigm and examined the vulnerability of the verifiability approach to countermeasures. For this purpose, we collected written statements from 44 mock criminals (liars) and 43 innocents (truth tellers), whereas half of them were told before writing the statements that the verifiability of their statements will be checked. Results showed that 'informing' encouraged truth tellers but not liars to provide more verifiable details and increased the ability to detect lies. These findings suggest that verifiability approach is less vulnerable to countermeasures than other lie detection tools. On the contrary, in the current experiment, notifying interviewees about the mechanism of the approach benefited lie detection.

We tested the accuracy of Scientific Content Analysis (SCAN), a verbal lie detection tool that is used world-wide by federal law enforcement and military agencies. Sixty-one participants were requested to write down the truth, an outright lie or a concealment lie about activities they had just completed. The statements were coded with SCAN and with another verbal lie detection tool, Reality Monitoring (RM). RM discriminated significantly between truth tellers and outright liars and between truth tellers and concealment liars, whereas SCAN did not discriminate between truth tellers and either kind of liar. Implications of the findings for the suitability of SCAN as a lie detection tool are discussed.

This study examined the role of memory for crime details in detecting concealed information using the electrodermal measure, Symptom Validity Test, and Number Guessing Test. Participants were randomly assigned to three groups: guilty, who committed a mock theft; informed-innocents, who were exposed to crime-relevant items; and uninformed-innocents, who had no crime-relevant information. Participants were tested immediately or 1 week later. Results showed (a) all tests detected the guilty in the immediate condition, and combining the tests improved detection efficiency; (b) tests' efficiency declined in the delayed condition, mainly for peripheral details; (c) no distinction between guilty and informed innocents was possible in the immediate, yet some distinction emerged in the delayed condition. These findings suggest that, while time delay may somewhat reduce the ability to detect the guilty, it also diminishes the danger of accusing informed-innocents.

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