When Will an Expert's Opinion be Shown to be Based on their Specialised Knowledge?

In Lang v The Queen [2023] HCA 29, the High Court considered whether a forensic pathologist’s opinion – that the deceased’s wounds were more likely inflicted by another person than self-inflicted – was founded on their expert knowledge within the field of forensic pathology (and thus, whether the opinion was admissible as expert opinion evidence). This case provides a solid illustration of an opinion which is demonstrated to be based on expert knowledge even though the process of reasoning was not particularly clearly expressed. To that extent, it also demonstrates the distinction between ‘sufficient reasoning’ to demonstrate that the opinion is substantially based on expert knowledge, as compared to ‘cogent or convincing reasoning’ which chiefly goes to weight but can also affect probative value. The case is also interesting because it speaks to and demonstrates a number of commonalities between the common law and Uniform Evidence Law tests for admissibility of expert opinion. A consequence of this is also that it is relevant to those practicing in all Australian jurisdictions.