The Full Federal Court decision in PAC Mining Pty Ltd v Esco Corporation FCAFC 18 highlights the care which must be taken in preparing evidence on the question of obviousness and the consequences of inappropriately instructing expert witnesses.
At trial (Esco Corporation v PAC Mining Pty Ltd  FCA 640), Tamberlin J found that PAC had infringed one of two patents owned by Esco in relation to wear assemblies for excavator buckets. His Honour also dismissed PAC’s revocation suit. PAC appealed the finding of infringement and also the finding that the claims were not obvious and therefore involved an inventive step.On the question of obviousness, it was accepted that an existing apparatus, referred to as Toplok was common general knowledge in Australia and that the inventive departure from Toplok consisted of the introduction of an adjustment assembly into the locking mechanism of that apparatus. Accordingly, the issue was whether it would have been obvious to the notional skilled person in the art that an improvement could be made to Toplok by the utilisation of the adjustment assembly claimed. Evidence on obviousness was provided by one of the inventors, McClanahan, on behalf of the Esco, and by an expert witness, Wightley, on behalf of PAC.
In relation to the evidence of McClanahan, the trial Judge, in reliance on a statement appearing Terrell, The Law of Patents (14th ed., 1994), noted that “when deciding whether there has been an inventive step the courts have attached considerable weight to the evidence of the inventor”. This statement was attacked on appeal by PAC. The Full Court referred to the High Court decision in Wellcome v VR Laboratories, stating that it was clear from that authority that:
there is no general proposition of law that, when questions of obviousness are in issue, considerable weight should be given to the evidence of the inventor
However the Full Court found that while the trial Judge was in error in according special weight to the evidence of McClanahan, this error did not materially effect the conclusion reached.
In relation to the evidence of Wightley, the trial Judge concluded that it was “reduced in weight by hindsight assumptions related to the nature of the problem, the need for a new design and the solution ultimately developed”. This conclusion was based on the fact that prior to expressing his opinions, Wightley was shown the Toplok technology and each of the patents in suit. He was also asked to assume that, at the priority date, it was well-known that the Toplok apparatus had a problem in that the lock itself was prone to work loose.
The Full Court considered that the approach of the trial Judge in treating the evidence of Wightley with caution was both justified and desirable, in light of various High Court decisions, including Hassle v Alphapharm and Lockwood v Doric (No 2). In affirming the decision of the trial judge that the claims were not obvious, the Full Court concluded that:
the thrust of his Honour’s reasons was to reject the evidence of Prof Whiteley because his opinion had been inappropriately tainted, from the outset … nothing put to us on appeal persuades us that his Honour was in error to have proceeded in this way.
The Courts have consistently warned against the dangers of hindsight analysis when assessing the question of obviousness. As such, it is imperative that evidence led to show that an invention is obvious is not tainted by hindsight and expert witness evidence must be prepared with care to ensure that it is not open to criticism of this kind.