Canadian Criminal Evidence/Credibility/Disreputable and Unsavoury Witnesses

General Principles
A "Vetrovec warning" refers to the special consideration required when considering the reliability of evidence from disreputable or unsavoury witnesses.

A jury must be given a "clear and sharp warning" with respect to the testimony of disreputable or unsavoury witnesses. This is known as a "Vetrovec" warning. This requires that:
 * 1) the evidence of certain witnesses is identified as requiring special scrutiny;
 * 2) the characteristics of the witness that bring his or her evidence into serious question are identified;
 * 3) the jury is cautioned that although it is entitled to act on the unconfirmed evidence of such a witness, it is dangerous to do so; and
 * 4) the jury is cautioned to look for other independent evidence which tends to confirm material parts of the evidence of the witness with respect to whom the warning has been given.

Applicable Witnesses
The warning should be applied for the testimony of accomplices and "disreputable witness of demonstrated moral lack" such as "a witness with a record of perjury".

A drug addiction at the time of the offence does not warrant a witness to be subject to a vetrovec warning.

Vetrovec Warning
"confirmatory evidence" should be independent and reliable. does not need to confirm every aspect of the case but rather should corroborate significant parts of the evidence.

Factors the court should consider when counsel requests a Vetrovec warning:
 * 1) The Vetrovec warning is designed to alert the trier of fact to the need for special attention when assessing the credibility of certain unsavoury witnesses.
 * 2) It is a clear and sharp warning to alert the trier of fact to the risk of adopting, without more, the evidence of an unsavoury witness
 * 3) The warning assigns unsavoury witnesses a special status, namely, it sets them apart from other witnesses and encourages an assessment of their credibility bearing in mind the unique reliability concerns they bring to a trial.
 * 4) The purpose of the Vetrovec warning is to alert the trier of fact that there is a special need for caution in approaching the evidence of certain witnesses whose evidence plays an important role in the proof of the accused’s guilt.
 * 5) There are four stages that ought to be considered when approaching the testimony of a potentially unsavoury witness, namely:
 * 6) the evidence of certain witnesses is identified as requiring special scrutiny;
 * 7) the characteristics of the witness that bring his or her evidence into serious question are identified;
 * 8) the trier of fact is cautioned that although it is entitled to act on the unconfirmed evidence of such a witness, it is dangerous to do so;
 * 9) the trier of fact is cautioned to look for other independent evidence which tends to confirm material parts of the evidence of the witness with respect to whom the warning has been given.
 * 10) There are no hard and fast rules in determining whether a witness is deserving of a Vetrovec warning. However, as the importance of the witness to central issues at trial increases, and the credibility concerns rise, so does the need for a caution.

See also: Tymiak, 2009 BCCA 98 at 30 to 32

The judge had wide discretion on whether to give a Vetrovec warning.

Where the witness provides "mixed" evidence that gives a significant amount of evidence that is helpful for the defence as well as the crown, the judge has the discretion whether the still invoke the warning.