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Where the prosecution case relies to a large extent on the identification of the defendant as the perpetrator, the judge should warn the jury of the need for caution in interpreting the evidence of the identifying witnesses. The judge should point out that a witness can be quite certain in his own mind, and very confident of his identification, and yet still be mistaken.

In R v clifton (1986), Lord Lane CJ emphasised that the Turnbull direction should expose the weaknesses in the indentification evidence in the specific case, as well as problems with identification in general.