Making sure witnesses are reporting information they observed themselves.
Advice on information exposure – guideline
After taking an initial account, officers and staff should consider advising witnesses that exposure to other sources of information about the event may affect their recollection and where possible it should be avoided. If it is unavoidable, the witness should be advised to make a note of the sources.
Sixteen studies tested the effects of co-witness discussion on recall accuracy. Fourteen of those studies found that witnesses were significantly more likely to report information they had not directly observed during an event when they were exposed to co-witnesses who shared what they had witnessed. This effect was also consistently observed in 13 experiments when the misleading information was presented as a written narrative (eg, a mock media report). Exposure to misleading information can lead to an overall reduction in accuracy. The Guideline Committee felt that, with particular regard to social media, news outlets and conversations relating to the incident, a note should be made of information sources to help witnesses think about the source of their memories if questioned later.
Evidence suggests that, if exposed to verbal or written information about an incident, witnesses can be susceptible to reporting that information, even if they did not observe it themselves. Advising witnesses could make them aware of this risk and might help them to think about the source of their memories if questioned later. It is recognised that asking witnesses to record full details of where they heard additional information about the incident may not be practical.