Undertaking Effective Investigations A Guide for National Human Rights Institutions Other possible witnesses may have included anyone who provided use of force training to QPS officers, as well as anyone involved in any previous similar situations involving any party, including S/Sgt. Hurley. Investigators should have considered a witness canvass at the scene of the arrest and in the area of the watch-house. It is not clear if this was done. KEY POINTS: CHAPTER 6 • Every effort must be made to identify possible witnesses. Failure to do so may compromise the investigation. • It is important to document the steps taken to identify and contact possible witnesses in order to demonstrate that every effort was made by the NHRI. • Use a broad range of canvassing techniques to identify possible witnesses. • Where circumstances prevent all those identified from being interviewed, interview those people whose evidence will have the greatest significance. 48