A reminder of the current Australian principles regarding immunity from civil suit for expert witnesses appears in Application of Michael Bar-Mordecai  NSWSC 414.
Mr Bar-Mordecai again sought to issue proceedings against Dr XY, with the proposed claim including allegations of breach of duty of care in respect of his conduct as a witness giving evidence in writing and orally, at NSW Medical Tribunal hearings regarding Mr Bar-Modecai’s application for re-registration as a medical practitioner.
The Court revisited the principles as follows:
18 Since the decision in R v Skinner (1772) Lofft 54 at 56; 98 ER 529, there has been embedded in the common law a principle of immunity of a witness from suit. In Skinner, Lord Mansfield said at 530:
“… neither party, witness, counsel, juror or judge can be put to answer, civilly or criminally, for words spoken in office.”
19 In Cabassi v Vila  HCA 41; (1940) 64 CLR 130, Starke J said at 140:
“No action lies in respect of evidence given by witnesses in the course of judicial proceedings however false and malicious it may be, any more than it lies against judges, advocates, or parties in respect of words used by them in the course of such proceedings or against jurors in respect of their verdict.”
20 In the same case, Williams J (with whom Rich ACJ agreed) said at 149:
“It is clear law that a witness cannot be sued in a civil action in respect of anything which he has said in the course of his examination in the witness box.”
21 Most recently, the High Court of Australia in D’Orta Ekenaike v Victoria Legal Aid  HCA 12; (2005) 223 CLR 1 said at  this:
“No action lay, or now lies, against a witness for what is said or done in court. It does not matter whether what is done is alleged to have been done negligently or even deliberately and maliciously with the intention that it harmed the person who would complain of it. The witness is immune from suit and the immunity extends to preparatory steps.”