NSW Criminal Law Trial - Sue Professional Witness Who Made Mistake?

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20 April 2015
Question: Can you sue a professional witness if their opinions were clearly wrong, yet they still convinced the jury my brother was guilty? The Professional Witness in his criminal law case made a mistake, which he can prove now, and gave a wrong opinion which the jury probably acted on to find him guilty?

Also can he sue his Representative for not following his wishes or instructions in his pre trial?

Tracy B

Well-Known Member
24 December 2014
Hi Katriona,

What evidence do you have that the professional witness' conclusion is clearly wrong?

For the evidence to influence the jury, it will have been assessed by the judge presiding over the trial that:
  • The expert witness is qualified to give their opinion on the matter;
  • The expert witness is credible (i.e their are clearly biased);
  • The opinion given by the expert witness is reliable (including an analysis of the type of expert evidence given, the conclusion drawn, the methodology used in coming to this conclusion, any other explanations for the result apart from the conclusion, how established is the field of study)
Any expert witness called by the prosecution (or police) can be cross examined by the defence. Therefore, what happened during cross-examination?

If you believe this opinion should not have been admitted into court, or that the jury was incorrectly/inadequately directed by the judge in relation to the evidence (based on law, not on your own opinions) then the defendant can lodge an appeal based on this ground. However, the error must be materially significant, in that, the error could have changed the outcome of the trial (conviction) or sentence. This is the best way to challenge the evidence of an expert. One cannot sue the expert who gives evidence.

The defendant can bring a negligence action against his representative (or lawyer) for failing to follow his instructions