A note of caution about expert witnesses

On 12 May 2008, Tambelin J of the Federal Court handed down a decision in Esco Corporation v PAC Mining Pty Ltd [2008] FCA 640. Amongst other findings, his Honour gave significantly reduced weight to the evidence of the expert witness put forward by the respondent on the question of obviousness on the basis that he had been provided with a copy of the patent in suit prior to giving his evidence. At paragraph 83, his Honour commented that:
"a posteriori reasoning, which starts with an understanding of the solution to a given problem and then seeks to draw a conclusion as to how obvious it was to reach that solution, has been correctly criticised by the Courts. Where both the problem and the solution are put before a person from the outset, it becomes a simpler task to reason backwards from solution to problem, which may lead that person to draw an incorrect or flawed conclusion as to obviousness of the solution."