Evidence: Relevance, Proof and Exclusion
Relevance and admissibility
Evidence must be relevant to be admissible. Relevance is a threshold test: does the evidence rationally affect the probability of a fact in issue? Even relevant evidence may be excluded by exclusionary rules or judicial discretion.
Witnesses and documents
Know examination-in-chief, cross-examination, and re-examination. Leading questions are generally not allowed in chief. Hearsay is an out-of-court statement tendered to prove the truth of its contents; exceptions include admissions, business records, and res gestae. Opinion evidence is generally inadmissible unless from an expert. Character and tendency evidence are tightly controlled.
Burdens and standards
In criminal trials, the prosecution bears the legal burden beyond reasonable doubt; the defence bears evidential burdens for some defences. In civil trials, the balance of probabilities applies.
Traps
- Confusing relevance with weight.
- Treating all hearsay as inadmissible; exceptions are common.
- Forgetting that propensity evidence requires significant probative value.
- Missing that judicial discretions can exclude otherwise admissible evidence.
Worked example
A witness testifies that a bystander said, 'The blue car ran the red light.' If tendered to prove the blue car ran the light, it is hearsay. If tendered to prove the bystander was present and able to speak, it may be admissible for that limited purpose. The trial judge should direct the jury on the limited use.