During the forum on Tuesday, there was discussion about why Darren Wilson was not interviewed for a few days after shooting Michael Brown. Former U.S. Attorney Jenny Durkan said that many police unions have negotiated a term in their contracts that provides for a delay of two or three days before questioning after a shooting incident, based in part on studies that suggest that memory would be better after the delay. Jeffery Robinson observed that civilians who are involved in shooting incidents might also experience psychological stress, but police investigators don't wait three days to interview them.
Here's a little more information on that issue:
- In some states a statute gives officers a period to obtain counsel before they are interrogated. See Kevin M. Keenan & Samuel Walker, An Impediment to Police Accountability? An Analysis of Statutory Law Enforcement Officers' Bills of Rights, 14 B.U. Pub. Int. L.J. 185, 212-14 (2005) (links are to HeinOnline).
- The Officer-Involved Shooting Guidelines
from the International Association of Chiefs of Police Psychological Services Section (2013) provide:
While officers may be asked to provide pertinent information soon after a shooting to aid the initial investigative process, whenever feasible, officers should have some recovery time before providing a full formal statement. Depending on the nature of the incident, the demands on the agency, and the emotional and physical status of the officers, this can range from a few hours to several days. An officer’s memory will often benefit from at least one sleep cycle prior to being interviewed leading to more coherent and accurate statements.3 4 5 6 7 Providing a secure setting, insulated from the press and curious coworkers, is important during the interview process.
p. 6 (citing articles about sleep and memory).