SMU Law Review
ORCID (Links to author’s additional scholarship at ORCID.org)
Abstract
The Federal Rules of Evidence (FRE) play a critical role in federal trials by determining what evidence the jury will be allowed to hear. Nonetheless, the rules are largely premised on untested psychological assumptions. The Present Sense Impression Rule (PSIR), for example, is an exception to the general ban against hearsay based on the assumptions that statements about contemporaneous events have fewer memory errors; are less likely to be lies; and, when they are lies, that listeners are better able to detect the lie than if the declarant has had time to prepare.
The rule, in other words, is based on assumptions that can be empirically tested. This Article surveys the scientific literature for insight into whether PSI statements have fewer memory errors and uses novel behavioral paradigms and electroencephalography (EEG) measures to test whether substantial contemporaneity is a safeguard against deceit. I conclude that PSI statements are likely to have fewer memory errors and the experimental results suggest that true contemporaneity, but not “substantial” contemporaneity, offers a degree of protection against deceit. Furthermore, the lies that do occur align with the protections inherent to the PSIR, with contemporaneous lies being more detectable by a third-party observer and lies about past events being susceptible to effective cross-examination.
Specifically, the results of the first experiment suggest that people switch cognitive strategies when lying about a contemporaneous event compared to a past event, employing a less working-memory-intensive strategy when given a delay. This switch lessens behavioral tells but may come at a cost to the overall memory of the event. The second experiment finds that even in a more behaviorally complex paradigm, individuals made significantly fewer errors and lied significantly more often when given a delay as short as three seconds to prepare their response, compared to a truly contemporaneous response prompted within 500 milliseconds.
Together, the results of the experiments suggest that the PSIR has a legitimate behavioral and cognitive basis: individuals switch between distinct cognitive strategies when lying about contemporaneous events compared to past events in a manner that supports the assumptions of the PSIR. The results also suggest, however, that this switch occurs almost immediately, and so the PSI exception should be restricted to only statements describing truly contemporaneous events.
Recommended Citation
Christopher S. Sundby,
The Neuroscience of Evidentiary Rules: The Case of the Present Sense Impression,
78
SMU L. Rev.
827
(2025)
