Generally, the court will order the parties to exchange witness statements for all witnesses of fact that are due to attend trial. The purpose of the witness statement is to set out in writing the evidence of the maker of the witness statement which is relied upon by the party calling that witness. The court may order that the statements are limited in length or by subject. A witness statement must not contain irrelevant or inadmissible material. It must contain the truth on the issues covered and contain a signed statement of truth.
Often a witness statement will simply be read by the judge during their preparation for the trial. However, the court may require all evidence to be given live orally in court, especially where the statements of fact are contentious.
Witness statements must be prepared with care to ensure they cover the relevant points which the party calling that witness needs to prove for their case. The judge can refuse permission to ask supplementary questions.
A witness called to trail to give evidence will usually be cross-examined so its contents must be accurate and complete.
From time to time, it is necessary to call expert evidence to prove or disprove a particular issue. Generally, expert evidence is opinion evidence based on certain assumed facts. If the facts are disputed, the expert may be asked to give alternative opinions based on a different set of facts.
An expert witness does not act for the party that hires them. An expert has an overriding duty to assist the court on the matters within their expertise. This duty overrides any obligation to the party that instructs and pays the expert. Expert evidence presented to the court should be independent. A party must obtain the courts permission to call an expert. And the court will decide whether an expert is necessary. The court will restrict expert evidence to that which is reasonably required to resolve the matter. The substance of the evidence will be given to the other party prior to trial.
In certain situations, the court will appoint a single expert as the court expert which will be jointly paid for by the parties.
At the end of the expert report there must be a statement by the expert confirming they understand their duty to the court and that they have complied with that duty. The report must also state the substance of all instructions both written and oral on which the report was written.