The Cautionary Rule

In the law of evidence, what is the cautinary rule and how is it a safeguard against unreliable evidence?

In any legal proceedings, the reliability of evidence is paramount. Courts cannot afford to make findings based on testimony or proof that is inherently suspect. It is from this fundamental concern that the cautionary rule emerges. However, what exactly is the cautionary rule?

The cautionary rule is a rule of practice, developed through case law rather than legislation, that obliges courts to approach certain categories of evidence with heightened vigilance. It operates in two distinct but related parts.

The first part requires the court to recognise when it is dealing with evidence that judicial experience has shown to be potentially unreliable. The second part requires the court to seek some safeguard or reassurance i.e., a factor that supports the conclusion that, despite its suspicious nature, the evidence in question can safely be relied upon.

Importantly, the rule is not a mechanical formula. As affirmed in S v Snyman,¹ a cautionary approach must not replace the exercise of common sense. The rule provides guidance, not a rigid checklist. The purpose of the cautionary rule is straightforward: to prevent courts from convicting or finding against a party on the basis of evidence that tends, by its very nature, to be untrustworthy. By compelling courts to seek corroboration or another form of reassurance, the rule ensures that judicial officers actively confront the potential weaknesses in the evidence before them, rather than accepting it at face value.

Compliance with the cautionary rule’s second requirement can be achieved in a variety of ways. Corroboration is the most common safeguard, but the list is not closed. Courts have accepted several other indicators of reliability, including:

The accused’s failure to testify
False evidence given by the accused
The fact that a potentially unreliable witness implicated someone close to them, suggesting no ulterior motive²

Categories of Evidence Attracting the Rule

1. Accomplices and Co-Accused

Perhaps the most well-known application of the cautionary rule concerns accomplice witnesses. An accomplice, someone who participated in the crime but did not perpetrate it, has both a possible motive to lie and the intimate knowledge of the crime’s details needed to do so convincingly. The prospect of indemnity under section 204 of the Criminal Procedure Act³ may provide a further incentive to fabricate or exaggerate. For this reason, courts require corroborating evidence that directly implicates the accused before relying on accomplice testimony.

The principles were helpfully summarised in S v Masuku:⁴ caution is imperative; corroboration must implicate the accused, not merely confirm the details of the crime; and if no corroboration exists, there must be some other indication of the witness’s reliability.

2. Single Witnesses

Section 208 of the Criminal Procedure Act permits conviction on the evidence of a single competent witness. However, the cautionary rule requires that such evidence be substantially satisfactory in every material respect, or else be corroborated. The test, as set out in S v Sauls,⁵ is not perfection. Shortcomings in testimony do not automatically preclude reliance on it. What matters is whether the court is satisfied that the witness told the truth and whether guilt has been established beyond reasonable doubt.

3. Children

The cautionary rule historically applied automatically to children’s evidence, on the assumption that children were imaginative and susceptible to suggestion. This automatic application has been widely criticised, and the South African Law Commission recommended its abolition. Recent judgments have rejected the blanket assumption that children are unreliable witnesses. What courts now consider instead are factors such as the child’s age and developmental stage, and whether the child was sworn in, while accepting that young children may still require substantial confirmation of their accounts.

4. Identification Evidence

Even an honest and credible witness can misidentify a suspect. As the court in S v Mthetwa⁶ observed, it is not enough for an identifying witness to be honest. The reliability of their observation must also be tested. In-court identifications carry little probative value, since the accused is typically already in the dock. Formal identification parades, when properly conducted, are more reliable.

5. Sexual Offences

For many years, complainants in sexual offence cases were subjected to the cautionary rule on the assumption that women were particularly prone to fabrication. This was decisively rejected in S v Jackson,⁷ which held that the rule rested on an irrational and outdated stereotype. Section 60 of the Criminal Law (Sexual Offences and Related Matters) Amendment Act⁸ subsequently codified this position, thus prohibiting courts from treating a complainant’s evidence with caution solely because of the sexual nature of the offence.

Conclusion

The cautionary rule remains a vital, if nuanced, safeguard within the law of evidence. Where multiple grounds for caution arise simultaneously, for instance, a child who is also a single witness giving identification evidence, courts must apply their minds separately to each applicable category. The rule does not operate as an automatic bar to conviction; rather, it demands that courts engage consciously and deliberately with the reliability of the evidence before them, and that they seek reassurance where the law requires it.

Written by Theo Tembo