Tendency evidence is some of the most potent material a prosecutor can put before a jury. It tells jurors that the accused has acted in a particular way before, inviting them to reason that the accused likely acted the same way again. Because that chain of reasoning carries real risks, the law imposes a strict gatekeeping test before any such evidence can be heard. That test is the probative value assessment under the Evidence Act 1995 (NSW), and passing it is the central hurdle for any party seeking to use tendency evidence at trial.
What the test actually requires
Section 97 of the Evidence Act 1995 (NSW) sets two threshold conditions. First, the party seeking to rely on tendency evidence must give reasonable notice. Second, the court must be satisfied that the evidence has significant probative value. That second condition is the substantive one.
Section 101 adds a further filter for tendency evidence led by the prosecution in a criminal trial. The court must find that the probative value of the evidence substantially outweighs any prejudicial effect it may have on the defendant. Both conditions must be met before the jury hears a word of it.
These are not low bars. "Significant" probative value under section 97 means more than a trifling or merely marginal relevance. "Substantially outweighs" under section 101 means the scales must tip clearly and demonstrably in favour of probative value, not just balance evenly.
How courts measure probative value
Probative value turns on the strength of the logical connection between the past conduct and the fact in issue. Courts look at several concrete features of that connection.
Specificity matters most. The more precisely the past conduct mirrors the conduct alleged in the current charge, the stronger the inference that both acts share a common cause in the accused's character or disposition. A single generic similarity carries little weight. A cluster of distinctive, unusual features shared across multiple incidents carries a great deal.
The High Court's reasoning in Hughes v The Queen [2017] HCA 20 is the current reference point. The Court held that tendency evidence has significant probative value when the similarities between past and present conduct are not adequately explained by coincidence. The more improbable the coincidence, the stronger the probative force of the evidence.
Proximity in time can also influence the assessment. Conduct from two years earlier generally has more probative force than conduct from twenty years earlier, because disposition evidence assumes some continuity of character. Courts don't apply a fixed cut-off, but time gap is a factor that both parties will address at a tendency evidence ruling hearing.
How courts measure prejudicial effect
Prejudice under section 101 is not simply the fact that the evidence is damaging to the defence. All prosecution evidence is damaging. The relevant prejudice is unfair prejudice: the risk that jurors will use the evidence for a purpose the law does not permit.
Three species of unfair prejudice appear most often in tendency arguments. The first is reasoning prejudice, where jurors convict because they think the accused is a bad person rather than because the evidence proves the specific charge. The second is distraction, where the jury focuses so much on the past conduct that it loses sight of the current allegations. The third is moral contamination, where the jury's revulsion at the past conduct colours every subsequent assessment they make.
A tendency direction given at the close of evidence is intended to address these risks, but courts have recognised that directions cannot always cure prejudice that is sufficiently entrenched by the time the jury retires.
The balancing exercise in practice
The balancing exercise is not mechanical. It calls for an evaluative judgment about the realistic way a jury is likely to use the material. Courts have identified some patterns that tend to affect the outcome.
Where the tendency evidence comes from a different complainant in a multi-complainant case, its probative force is often high because independent corroboration reduces the risk of coincidence or contamination between witnesses. That same feature also reduces moral prejudice, because the jury is assessing real, documented conduct rather than a bald assertion of general bad character.
Where the tendency evidence is the only substantial evidence of guilt, courts apply the section 101 filter with particular rigour. Tendency evidence cannot do the whole job of proof by itself without approaching the very reasoning error the rule is designed to prevent.
Judges also consider whether the evidence can be redacted or adduced in a form that preserves its probative force while stripping away material that is gratuitously prejudicial. If a sanitised version satisfies section 101, that is usually the version that gets in.
What happens after the test is decided
If the court is satisfied that probative value substantially outweighs prejudicial effect, the evidence is admitted and the trial proceeds. The judge will then need to give a careful direction at the appropriate point, telling the jury the precise purpose for which the evidence can be used and the purposes for which it cannot.
If the evidence fails the test, it is excluded entirely. The prosecution cannot reference it in opening, lead it through witnesses, or use it in closing. An accidental reference to excluded tendency evidence can ground a mistrial application.
Where a ruling goes against the defence, the admissibility decision itself can become a ground of appeal. Because the probative value assessment involves a discretionary judgment, an appellate court will not simply substitute its own view. It will look for error in principle or a conclusion that no reasonable judge could reach on the material before the court.
Raising a timely and well-structured tendency evidence objection is the mechanism through which defence counsel challenges this ruling before evidence is led. Getting that challenge right, and preserving the issue for appeal if necessary, requires careful preparation well before the trial begins.