Smith & Nephew Plc v Convatec Technologies Inc

Inventive step is determined by the statutory question whether the claimed invention was obvious to the skilled person at the priority date. A structured approach is a useful aid, but no verbal formula replaces that question. Whether a route was obvious to try, including its prospects of success, is only one consideration among all the circumstances. It is not an independent sequence of hurdles. In a technical field where the skilled team would not experiment without understanding the rationale, a simple test may still be non-obvious where competing explanations make one outcome likely to fail and another uncertain. An appellate court should respect a trial judge’s assessment of the evidence unless an error of principle is shown.

Smith & Nephew appealed from the decision of HHJ Birss QC in the Patents Court. Convatec’s patent for preparing light-stabilised antimicrobial wound-dressing materials was invalid as granted, but Convatec sought amendment. The judge allowed the amendment and rejected attacks based on added matter, obviousness and insufficiency. On appeal, Smith & Nephew challenged only the finding that the amended claim was not obvious over Kreidl, a 1946 publication concerning light-stable silver-halide disinfectant preparations. The central issue was whether applying Kreidl’s method to modern gel-forming fibres, such as Aquacel, would have been obvious at the priority date.

Appeal dismissed. Lord Justice Kitchin gave the judgment, with Lord Justice Jackson and Lady Justice Arden agreeing.

1. The statutory test under the Patents Act 1977, sections 1(1) and 3, is whether the invention was obvious to the skilled person having regard to the state of the art at the priority date. The structured approach in Pozzoli v BDMO SA [2007] EWCA Civ 588 is convenient but not essential. The statutory question must remain central.
2. Whether it was obvious to try a particular route with a fair or reasonable expectation of success may be relevant. It is not a separate hurdle or a substitute for the statutory test. The court must assess all relevant circumstances, including the possible research avenues, motivation, effort and expectation of success. Those considerations interact.
3. The trial judge was entitled to find that the skilled team would not carry out an experiment without considering its rationale. Kreidl disclosed the same basic method and a light-stable product, but it presented competing explanations. Stability might result from adsorption, physical shielding within cotton fibres, or both. The common general knowledge did not support the adsorption theory, while physical shielding offered no prospect of success with Aquacel, which lacked the relevant internal structure. If adsorption were responsible, success with Aquacel remained uncertain.
4. The ease of performing the proposed test did not make it obvious. In the circumstances, the judge was entitled to conclude that the skilled team would not simply try the method and see. His reasoning did not require certainty or a guarantee of success. It answered the correct question: whether applying Kreidl’s method to Aquacel was obvious.
5. The appellate court found no error of principle in the judge’s assessment of the expert evidence or the technical teaching. His conclusion that the amended claim was valid over Kreidl was one he was entitled to reach.

• Court of Appeal (Civil Division): The appeal was dismissed. The court upheld the finding that the amended patent claim was not obvious over Kreidl.
• High Court, Chancery Division (Patents Court): In [2012] EWHC 1602 (Pat), HHJ Birss QC allowed amendment of the patent and rejected the attacks on its amended form.