27—How far a party may discredit his or her own witness
A party producing a witness shall not be allowed to impeach his credit by
general evidence of bad character; but if the judge is of opinion that the
witness is adverse, the party may—
(a)
contradict the witness by other evidence; or
(b) with
the permission of the judge, prove that the witness has made, at any other
time, a statement inconsistent with his present testimony: Provided that,
before giving such last-mentioned proof, the circumstances of the supposed
statement sufficient to designate the particular occasion, must be mentioned
to the witness, and he must be asked whether or not he has made the statement.