(1)  At the trial of a person accused of a crime under chapter XIV , XIVA or XX , no rule of law or practice shall require a judge to give a warning to the jury to the effect that it is unsafe to convict the person on the uncorroborated evidence of a person against whom the crime is alleged to have been committed.

(2)  A judge shall not give a warning of the kind referred to in subsection (1) unless satisfied that the warning is justified in the circumstances.