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All-out physical exertion in a threatening situation can seriously damage the memories of those involved for many details of the incident.

Researchers, led by Dr Lorraine Hope of the University of Portsmouth, found that less than 60 seconds of all-out exertion, as might happen when an officer is forced to chase-down a fleeing suspect or engage in a physical battle with a resistant criminal, can seriously impair their ability to remember details of the incident - or even identify the person who was involved. 
The findings, published in Psychological Science, a journal of the Association for Psychological Science, are a stark warning to police officers, police chiefs and the courts, according to Dr Hope, a Reader in applied cognitive psychology of the university's Department of Psychology.

She said, "The legal system puts a great deal of emphasis on witness accounts, particularly those of professional witnesses like police officers. Investigators and courts need to understand that an officer who cannot provide details about an encounter where physical exertion has played a role is not necessarily being deceptive or uncooperative. An officer's memory errors or omissions after an intense physical struggle should not unjustly affect his or her credibility."

Dr. Hope found those who had been asked to exert themselves physically remembered less about the target individual and made more recall errors compared to the control group of observers. The officers who had been exerted also recalled less about the initial briefing information and what they did report was less accurate. 

Officers who had been exerted reported less about an individual they encountered incidentally while en route to the trailer. While more than 90 percent of non-exerted observers were able to recall at least one descriptive item about him, barely one-third of exerted officers remembered seeing him at all.

Everyone remembered seeing the angry suspect in the trailer, but non-exerted observers provided a significantly more detailed description of him and made half as many errors in recall as those who were exhausted. These observers were also twice as likely to correctly identify the suspect from a line-up.