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One of the most troublesome areas in the law of evidence is that of identification. A defendant will very frequently not contest that an offense was committed, but deny that he was the person who committed it. If he does, then the prosecution will have to lead evidence that identifies him as the perpetrator. Most often, this evidence is an eye-witness account. However, such accounts are notoriously unreliable (see turnbull direction).

Pace Code of Practice D states that it is desirable to hold an identification parade if the witness has already given sufficient information for a tentative identification to be made. However, in practice the witness may be able to recognize the perpetrator, but not describe him well enough for the police to determine who he is. In such a case, the code Code allows the police to take the witness to the place where she saw the perpetrator, or where he is likely to be, so that she can pick him out. However, D3.2(a) indicates that, where practical, the police should record a description before undertaking this exercise. The reason for this is that witnesses usually want to be helpful, and there is a strong compulsion to pick somebody, so it is useful to have an alternative description as a comparison.

In RVKelly1998, the Court of Appeal held that breaches of Code D rendered identification evidence less reliable, and this might engage s.78 of PACE, giving the court a discretion to exclude the evidence. However, not all breaches of Code D would lead to exclusion. Where the language of the Code is mandatory, rather than expressed in terms of 'reasonable practicability', then non-compliance very like will lead to exclusion (R v forbes (2001)).