At common law, certain kinds of evidence were considered to be particularly unsafe. "Rules of practice" developed requiring the judge to
warn the jury of the dangers of convicting an accused person on the "uncorroborated" or unconfirmed evidence of certain witnesses. Moreover, judges had an obligation to describe for the jury when evidence was capable of "corroborating" the dangerous testimony, according to law. Judges even had to warn themselves in judge alone trials. According to these common law rules, triers of fact could convict in the absence of "corroboration," but only after receiving these mandatory warnings. The most important kinds of evidence singled out for this cautious treatment were the testimony of children, of accomplices to crime, and of complainants alleging sexual offences.
A number of statutes were passed making corroboration a "rule of law" in some cases, actually requiring that corroboration must exist before conviction. For example, section 133 of the Criminal Code provides that no person can be convicted of the offence of perjury "on the evidence of only one witness unless the evidence of that witness is corroborated in a material particular by evidence that implicates the accused."
The law of corroboration evolved into a highly technical and restrictive body of authority. Corroboration came to have a narrow meaning. Evidence would not be corroborative simply because it supported or confirmed the suspect testimony. Corroborative evidence had to be "independent," had to confirm the testimony in a material particular, and had to implicate the accused.4To be corroborative, circumstantial evidence had to be consistent only with guilt. In R. v. Ethier,5for example, the Crown offered evidence as corroboration during a rape prosecution that
1) human blood of a type matching the blood type of the complainant was found on the accused’s shorts,
2) hair similar to the complainant’s was found in his car,
3) the handle on his car was broken,
4) the accused’s clothing matched the description provided by the complainant, as did the licence number,
5) she had a bruise on her left cheek,
6) she was distraught immediately after the incident, and
7) marks were found in the car consistent with the claim by the complainant that there would be foot marks on the ceiling which were made by her while she was being assaulted.
The Ontario Court of Appeal held that none of this corroborated the rape allegation. Items (5) and (6) would be some evidence to con-
firm that a rape had occurred if the injuries and emotional condition were pronounced enough, but it did not confirm the identity of the accused as the rapist. Items (3), (4), and (7) were not corroborative because their relevance depended on the testimony of the complainant. In other words, as items of evidence they were not "independent" enough to be corroborative. As for items (1) and (2), these were equally consistent with the truth as with the falsity of her allegation because her hair and blood type could get where they were without her having been raped. While all of this evidence was admissible and might well support a conviction, the trial judge erred in law by failing to tell the jury that the evidence of the complainant remained uncorroborated.
Not surprisingly, the law of corroboration was criticized because of its technicality. It was also condemned in the case of sexual offence complainants and in the case of the testimony of children as being premised on antiquated and inaccurate assumptions that these witnesses are inherently unreliable. As a result, these common law rules of practice have been abandoned and a number of the statutory corroboration requirements have been repealed.
Some statutory corroboration rules (such as the perjury and Alberta Evidence Act unsworn evidence provisions referred to above) continue to apply. The trend in criminal cases is to limit the impact of such provisions. In R. v. B.(G.)6the Supreme Court of Canada held that a section calling for a child’s evidence to be "corroborated in a material particular by evidence that implicates the accused" did not require that the corroborative evidence implicate the accused. Instead it would be enough if there was independent evidence supporting the testimony needing corroboration, thereby making it safe to convict. Quoting Vetrovec v. R.,7which had dealt with common law and not statutory corroboration rules, the Court affirmed that "[t]he important question . . . is not how our trust [in the testimony] is restored, but whether it is restored at all."8While the Quebec Court of Appeal held in R. v. Neveu9that it would be wrong to apply the Vetrovec standard to all statutory provisions regardless of their wording,10the court interpreted the corroboration requirement for perjury strictly such that it would apply only if the Crown’s case was
based on the direct evidence of a witness rather than on circumstantial proof. In R. v. Eriksen the Yukon Territory Court of Appeal agreed and upheld the conviction of the accused based on his own out-of-court admissions.11While statutory language cannot be ignored, it is clear that the trend is to construe corroboration requirements into near oblivion. This is part of the more general movement away from technical corroboration requirements. The objective, subject to statutory limit, is to permit triers of fact to evaluate information free from inappropriate general assumptions about the lack of credibility of certain classes of evidence.
When the common law corroboration rules were dispensed with, they were replaced with rules giving judges the discretion to provide special warnings to jurors about the dangers of relying on the testimony of some Crown witnesses.12These cautions are meant to alert the jury to the risks involved.13They therefore apply solely in jury cases.14Warnings do not result in the loss of the evidence. Once trained, jurors can properly evaluate the information before them.15Although the decision to warn is "discretionary" if the testimony is dangerous enough in the particular circumstances of the case a failure to give an adequate warning to a jury will constitute an error of law. The greater the concern, the more likely a warning will become mandatory.16
In R. v. McCarroll, for example, it was mandatory to warn the jury about
a witness whose evidence was so central as to put the gun in the hands of the accused, and who lied about her outstanding fraud charges. This was particularly so because, given her role, she would likely strike the jury as the witness least implicated in events leading up to the killing.17Typically special warnings are called for where there are "defects in the evidence of a witness that may not be apparent to a lay trier of...