Sunday, 1 May 2016
Hatziandoniou v Ruddy [2015] NSWCA 234
“One of the benefits of expertise is that it enables the person who has the relevant ‘training, study or experience’ to extrapolate from the general to the particular.”



Section 79(1) of the Uniform Evidence Acts provides an exception to the Section 76 prohibition of opinion evidence:
‘If a person has specialised knowledge based on the person’s training, study or experience, the opinion rule does not apply to evidence of an opinion of that person that is wholly or substantially based on that knowledge.’
But how specific does this specialised knowledge need to be?
Magda Di Vincenzo, a Director in our Melbourne office, reviews a recent case that suggests that experts should be granted some latitude.


Hatzandoniou v Ruddy concerns a collision between a motorbike ridden by Mr Hatzandoniou (travelling south) and a truck driven by Mr Ruddy (travelling north). Mr Hatzandoniou claimed damages for his injury. 
At the trial, both parties claimed that the other was travelling on the wrong side of the road.
The court considered whether the presence, in the southbound lane, of a liquid discharged from the bike meant that it the collision occurred there; or in the northbound lane, with the liquid shed only after the bike had returned to its correct lane. 

The expert evidence

An expert, Mr B, was retained by Mr Hatzandoniou. Mr B is a mechanical and biomedical engineer. He gave evidence based, among other things, on his analysis of the discharged fluid, and concluded that the bike was correctly travelling in the southbound lane.
At trial Mr B was questioned about his training and experience. He said that he had:
  • studied fluid dynamics
  • not studied the flow of liquids from a motorcycle engine
  • based his opinions on the close correlation between motorcycle engines and motor vehicle engines in general with which he was very familiar.
The trial judge excluded a part of Mr B’s report saying:
“…he has never ever in his evidence tested the flow of liquid from a motorcycle engine, interpreted or tested the flow of liquids or done any testing which would enable him to express the opinions which he stated in para 8 of his report.
There is, therefore, in my opinion, no basis upon which I could conclude that the opinion which he has given … is based on his specialised knowledge, training, study or experience. Accordingly, part of [Mr B’s] report is not admissible.”
The appeal judge disagreed. He expressed the opinion that the primary judge took an “unduly narrow approach to the question of the qualifications of [Mr B]”. He also said:
“One of the benefits of expertise is that it enables the person who has the relevant ’training, study or experience’ to extrapolate from the general to the particular.”
He concluded that Mr B’s evidence had been wrongly excluded. He ordered a retrial to allow Mr B to be cross-examined and for the opposing expert’s evidence to be properly evaluated.


Experts can be asked for opinions on many highly specialised issues. If they were not allowed to generalise within their fields (within reason), it might sometimes be impossible to help the court with any expert evidence at all. The appeal decision in this matter shows that this outcome may be avoidable.