In deciding whether a question affecting the credibility of a witness is
relevant, or ought to be allowed, the judge shall have regard to the following
considerations:
(a) such
questions are proper if they are of such a nature that the truth of the
imputation conveyed by them would seriously affect the opinion of the court as
to the credibility of the witness on the matter to which he testifies;
(b) such
questions are improper if the imputation which they convey relates to matters
so remote in time, or of such a character, that the truth of the imputation
would not affect, or would affect only in a slight degree, the opinion of the
court as to the credibility of the witness on the matter to which he
testifies;
(c) such
questions are improper if there is a great disproportion between the
importance of the imputation made against the witness's character and the
importance of his evidence.