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Article by Linda Geven on knowledge of suspects published in Biological Psychology

The article deals with the physiological recognition of knowledge by suspects and whether this can be used to distinguish between true and false confessions.

Memory detection is a method to find out whether a suspect has knowledge that only the offender could know, compared to measuring deceitfulness in a standard polygraph test, says Geven. 'It is focussed fully on recognising specific details of a crime and can be used as a tool to make distinctions between several suspects. The test that I used in my article is also known as the Concealed Information Test (CIT) which was developed in 1959 by David Lykken. During the experiment, questions are asked about specific details of the crime scene and only the guilty suspect would recognise the correct answers.  Multiple choice questions are made usually giving five different options for answers: the correct details (for example the victim was strangled) and four plausible alternatives (for example the victim was shot or stabbed). The idea is that an innocent person cannot distinguish the correct answer from the alternatives and actually responds to each detail in the same way. The guilty suspect displays a physiological reaction on recognition of the murder weapon, such as the secretion of sweat on their hands.'

In this research article, Geven examined whether memory detection techniques can be applied to obtain a more accurate distinction between true and false confessions. 'In the experiment, test subjects were linked to a second participant who was actually a research assistant trained to tempt the participant to break the rules and cheat during the experiment. All test subjects, irrespective of whether they had cheated or not, were accused by the experiment supervisor and interrogated intensively.  The results of the memory detection test showed that only the participants who had given a true confession, in contrast to innocent participants who had (wrongly) confessed, displayed the physiological change that corresponds to knowledge recognition of a guilty suspect. So we could determine who had actually cheated in the experiment, and thus refute the false confessions. This study demonstrates the potential value of memory detection for verifying the validity of confessions. This is important, because we as humans are actually very bad at recognising lies. Unfortunately, research shows that police officers are also unable to flawlessly appraise the truth of confessions and that an incorrect interpretation can have far-reaching consequences.'

Linda Geven’s article is available open access.

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