Intentional retrieval suppression can conceal guilty knowledge in ERP memory detection tests

Abstract

Brain-activity markers of guilty knowledge have been promoted as accurate and reliable measures for establishing criminal culpability. Tests based on these markers interpret the presence or absence of memory-related neural activity as diagnostic of whether or not incriminating information is stored in a suspect's brain. This conclusion critically relies on the untested assumption that reminders of a crime uncontrollably elicit memory-related brain activity. However, recent research indicates that, in some circumstances, humans can control whether they remember a previous experience by intentionally suppressing retrieval. We examined whether people could use retrieval suppression to conceal neural evidence of incriminating memories as indexed by Event-Related Potentials (ERPs). When people were motivated to suppress crime retrieval, their memory-related ERP effects were significantly decreased, allowing guilty individuals to evade detection. Our findings indicate that brain measures of guilty knowledge may be under criminals' intentional control and place limits on their use in legal settings.

Keywords: Cognitive control; Episodic retrieval; Event-Related Potentials; Guilty knowledge; Memory suppression.

Fig. 1

Group average mid-parietal ERPs and scalp maps contrasting different item types within blocks in Experiment one (left column) and Experiment two (right column). Topographic maps show the mean difference between probes and irrelevants between 450 and 800 ms.

Fig. 2

Group average mid-parietal ERPs contrasting the same item types across blocks in Experiment one (left column) and Experiment two (right column).

Fig. 3

Percentage of participants classified as guilty using different statistics for the bootstrap test at different guilt classification thresholds.