The direction in R v Costin that the jury should not speculate about a complainant's motive to lie must be read subject to Palmer v The Queen: while absence of proof of motive is neutral, proof of a motive to lie weakens credibility, and the jury's attention must be adequately drawn to any evidence of motive and its impact on credibility. A Kilby direction is required where there is significant delay in complaint, particularly where the complainant had opportunity to complain or call for help at the time of the alleged offence.
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