Witness instructions are seen as a set script that is read off to witnesses before identification procedures.  These instructions help inform the witness that they do not need to make an identification if they cannot do so with confidence, explains that their input that a potential suspect may be innocent is just as important to convicting the correct perpetrator as the notion that they may be guilty, and that investigation will continue with or without their identification.  Research shows that this helps lift the pressure from witnesses who may think that they must make an identification whether or not they are fully confident in it.