The Neuroscience of Evidentiary Rules: The Case of the Present Sense Impression

Abstract

The Federal Rules of Evidence (FRE) determine what evidence federal juries see and don’t see, with most states having adopted rules modeled on the FRE. Despite playing a pivotal role in the accuracy, efficiency, and legitimacy of trials, the rules are premised on untested psychological assumptions. The Present Sense Impression (PSI), is an exception to the general ban against hearsay when it is believed that the traditional risks of errors in perception, memory, narration, and deceit associated with hearsay are lessened. The PSI assumes that contemporaneity is a safeguard against deceit. Here, we used novel behavioral paradigms and electroencephalography (EEG) measures to assess several event-related potential components (ERP) associated with deception. These ERPs were used to test the hypothesis assumed by the PSI exception that distinct cognitive processes underlie lies about contemporaneous events, lies about past events, and truthful responses. Our results suggest that while contemporaneity is not a safeguard against deceit per se, as the PSI assumes, people do switch cognitive strategies when lying about a contemporaneous event compared to a past event and that these strategies are well suited to the safeguards established by the PSI. Specifically, when lying in the moment individuals utilize a slower, more memory intensive lie cognitive strategy that may be more easily detected by a causal third party observer. When lying about a past event, however, individuals shift to a faster, less memory intensive cognitive strategy that may result in fewer behavioral tells but could signify less overall encoding of the event such that cross examination may be effective at uncovering the deceit.