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Hindsight in Expert Evidence – A Warning from the High Court

The UK High Court recently found a patent for a breathing tube to be valid and infringed on the basis of expert evidence submitted by the parties. The judge clearly preferred the evidence of one expert over the other and this was decisive for the case result.

The case concerned Fisher & Paykel Healthcare Limited's EP(UK) patent for expiratory limbs of breathing circuits. Fisher & Paykel (‘F&P') sued Flexicare Medical Limited and Flexicare (Group) Limited (together ‘Flexicare') for infringement. Flexicare admitted their products fell within the claims of the patent, but argued the patent was invalid and counterclaimed for revocation.

As part of their case, Flexicare submitted an expert report from Dr Dixon. Mr Justice Meade found there to be significant problems with Dr Dixon's report. The judge noted that there has been an heightened focus in recent years on the way in which expert evidence is prepared, and especially the sequence in which experts are shown documents. Ideally, experts should first be asked about the common general knowledge (CGK), then shown the prior art, and only then shown the patent in suit (following MedImmune). The courts recognise that this may be difficult in practice, as the expert may already be aware of the invention in the patent, for example from a patentee's commercial embodiment of it. Mr Justice Meade considered that in such cases, the expert must identify in their report how they knew about the invention and when, and to reflect carefully on how this might influence them. This was where Dr Dixon's evidence fell short of the judge's expectations.

Dr Dixon did acknowledge that he had seen the patent before, but said he only remembered this when shown the patent after he saw the prior art. In fact, Dr Dixon's exposure to the patent was considerably more extensive, something that had to be drawn out from him in cross-examination. He had long experience with F&P's products and knew the relevant features of them pertinent to this case. He even had his own patent application identifying solutions to problems that, he had to accept, could only have been a reference to F&P's products. Mr Justice Meade found that Dr Dixon's mere reference in his report to having seen the patent was inadequate because he had not thought about his previous knowledge of the alleged invention properly, indicating a lack of care about how his prior experience of the invention influenced his thinking on the issue of obviousness."

As a result, the judge determined that Dr Dixon's evidence was tainted by hindsight, impacting the weight given to this evidence throughout the judge's considerations on obviousness, most notably when contrasting Dr Dixon's evidence against the opposing expert evidence from F&P.

F&P's expert evidence was provided by Mr Pierro. During cross-examination by Flexicare, Mr Pierro gave evidence which appeared to support Flexicare's case of invalidity due to obviousness, which understandably Flexicare tried to rely on. Mr Justice Meade, however, was not convinced. The judge considered that the basis of the questions given to Mr Pierro injected hindsight by defining the skilled person very narrowly so as to have a very tight focus on the specific topic of the patent, and at the same time as wanting to find a different and better solution to the specific problem solved by the patent. As the judge noted, although the skilled person is deemed to read the prior art with care and interest, they do not have any expectation in advance that doing so will be useful. As a result, the judge looked more broadly at Mr Pierro's statements, and determined that he had not actually accepted the invention to be obvious, despite his apparent statement to the contrary. Ultimately the judge found the patent to be valid and infringed by Flexicare.

This case shows that the courts will take a keen interest in the way expert evidence is provided. If a judge is not satisfied that care has been taken to avoid hindsight, they may not take full account of the submitted expert evidence.