What is the current state of the law on special instruction in the defence of eyewitness identification?

40 But that concern can be met by casting the special instruction in language appropriate to the case. The precise point which has been made time and again is that there is no rigid formulation for such instruction. Each should be designed with specific reference to the evidence which either supports or casts doubt on the eyewitness identification. In some cases, because of the abundance of other supportive evidence, there will be need for little more than a cursory caution, pointing out as Lord Widgery C.J. suggested, the reason why such a warning is necessary and: ...the possibility that a mistaken witness can be a convincing one and that a number of such witnesses can all be mistaken. (at p. 137) In other cases, where supportive evidence is non-existent, and more than just the inherent weaknesses are obvious, a more strongly worded caution will be necessary, together with a careful review of all of the circumstances in the evidence which are relevant to that issue. In cases where the identification evidence is so weak as to be unreliable, the trial judge may be required to go so far as to tell the jury that it would unsafe to accept or to base a conviction upon it; Regina v. Mastin, supra, p. 220.