The general rule at common law is that all evidence which is sufficiently relevant to the issue before the court is admissible and all evidence that is irrelevant or insufficiently relevant is excluded (Hollington v F Hewthorn and Co Ltd  KB 587).
Not all relevant evidence is admissible for family law purposes and the Commonwealth Evidence Act (in particular) allows the exclusion of some relevant evidence under specific provisions.
Bases for exclusion of otherwise relevant evidence take many forms but include:
- the possibility the evidence is manufactured;
- procedural fairness;
- untested (or untestable) evidence;
- collateral issues; or
- the value of evidence is outweighed by unfairness, prejudice or delay.
Generally, the evidence of an individual can only include a description of something seen, heard or taken in through one of the senses – conclusions or suspicions cannot ordinarily be included.
Generally, evidence drawing conclusions or evidence of a specialised nature requiring particular expertise can only be provided by a suitably qualified expert.
The requirements for admissibility in the hearing of an interim application may be less stringent than those applying in relation to hearing of a final application.