The cognitive interview (CI) is a set of forensic evaluation procedures that has proven its efficiency. Nevertheless, little investigation has been made into its usage on witnesses with the intention of lying. With the aim of proving whether the efficiency of the CI is maintained where the witness is lying we carried out two experiments and we included instructions to tell the truth or to lie as independent variables. We used a 2 Type of interview (SI/CI))2 Statement Condition (True/ False))2 Interviewee Gender (Male/Female) design with 18 interviewers in a sample group of 240 gender-matched university students being interviewed and the classic measures from the CI as dependent variables: the total number of details, details of actions, details about people and details concerning objects. In a first experiment, participants who lied exculpated the protagonist of a film fragment from rape, whereas in a second, those who lied accused an innocent protagonist. The results, in accordance with previous studies, showed a globally better efficiency for CI. Nevertheless, analysing the material based on type of details, this efficiency is only found in details concerning actions and objects. We discuss the forensic importance of these findings.

The Memory Characteristics Questionnaire (MCQ) was developed by Johnson, Foley, Suengas, and Raye (1988) to assess the characteristics of memories of external and internal origin, postulated in the source monitoring model (Johnson, Hashtroudi, & Lindsay, 1993). The MCQ was translated into Spanish using a back-translation method. Psychometric properties of the translated MCQ were tested using responses collected from an experimental study simulating a forensic context. Ten police officers and 8 psychologists individually interviewed 240 university students who completed the MCQ after reporting what they had seen in a film. Half of the participants were asked to tell the truth, while the other half were asked to lie. The results have shown adequate psychometric properties of the Spanish MCQ items for the total sample and across experimental conditions. Cronbach's alpha value was .79 for the total sample, .78 for the honest condition, and .76 for the lie condition. Validity evidence of dimensionality supports that the factor structure of Spanish MCQ was equivalent to that proposed by the authors of the original version. Also, a two-factor ANOVA (video clip x condition) was performed to analyze experimental data. Neither interaction effects, F(236) = 1.189; p = .277, nor main effects were found to be significant between those asked to tell the truth and those asked to lie. These results demonstrate that the Spanish MCQ has adequate psychometric properties.

We describe two experiments designed to verify whether the source monitoring (SM) model categories and the cognitive interview (CI) contribute to distinguishing true from false statements. We used a 2 Type of Interview (Structured/ Cognitive) ) 2 Statement Condition (True/False) design with 18 interviewers in a sample group of 240 gender-matched university students being interviewed about a film fragment. In Experiment 1, participants who lied exculpated the protagonist from rape, whereas in Experiment 2 their lies were aimed at accusing an innocent person. As dependent variables we used criteria from the SM: details, supporting memories, thoughts and feelings and cognitive operations. The results suggest that the statements of honest participants interviewed using the CI provided more overall information than those obtained under any other condition. When a lie is aimed at exculpating someone from criminal behaviour, statements involve more cognitive operations and less sensory, temporal and contextual information, but only when the structured interview (SI) is used. When the lie is aimed at falsely accusing someone, the SI and the CI produce similar results. We discuss the forensic importance of these findings.

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