Panduit Corporation v Band-It Company Ltd.

Patent obviousness must be assessed through the eyes of the ordinarily skilled but unimaginative person, equipped with the relevant common general knowledge and practical mindset at the priority date. The court must avoid reconstructing a route to the invention from knowledge of its result.

The party alleging invalidity bears the burden of proving obviousness. Where expert evidence does not establish that the skilled person would have taken the alleged steps, the court should not assume them. Secondary evidence remains an aid to the assessment, but must be evaluated with the whole evidential case.

Commercial success is not the statutory test under the Patents Act 1977. Practical and commercial realities may nevertheless inform what technical possibilities would have occurred to the skilled person.

Panduit, the proprietor of a patent for a selectively coated metal ball-lock cable tie, appealed from a decision of the Patents County Court. The deputy judge held claims 1 to 5 invalid for obviousness, while finding that Band-It's ties would infringe those claims if valid.

The alleged inventive step was leaving the strap edges coated to prevent abrasion while leaving the ball-locking area uncoated. The judge reasoned that the skilled person would first coat the tie completely, discover reduced tensile strength, and then remove the coating in the locking area.

The appeal concerned whether that reasoning improperly used hindsight, failed to adopt the skilled person's practical mindset, and wrongly treated the secondary evidence as merely requiring rebuttal of a prima facie conclusion of obviousness.

1. Appeal allowed unanimously. Aldous LJ held, with whom Mance and Latham LJJ agreed, that Band-It had not established obviousness. The finding that the relevant claims were invalid was set aside. The unchallenged finding that the accused ties fell within claims 1 to 5 therefore remained material.

2. The structured approach in Windsurfing required the court to assess the difference from the prior art through the skilled person's knowledge and practical outlook at the priority date. The deputy judge correctly identified partial coating as the relevant difference. However, he did not adequately ask why coated ties were used and what that would mean to the skilled person.

3. The evidence showed that coating was understood to assist handling in cold conditions, avoid galvanic reaction and corrosion, and address actual or perceived abrasion. Removing coating from the locking area would undermine several of those practical purposes. In that context, it was not permissible, without relevant primary evidence, to assume that the skilled person would first fully coat the ball-lock tie and then remove coating from the locking zone.

4. The deputy judge's two-step reasoning was an impermissible ex post facto reconstruction. It began with the known invention and postulated a route to it. Having rejected both experts' evidence on obviousness, the judge also erred by treating the secondary evidence only as incapable of rebutting a prima facie conclusion. Band-It retained the burden of establishing obviousness on the evidence as a whole.

5. Mance LJ added that commercial worth is not itself the test under section 3 of the Patents Act 1977. Nevertheless, commercial and practical realities can affect the skilled person's mindset and the perceived limits of technical practicability. Here those realities supported the conclusion that the partially coated tie would not have occurred as an obvious solution.

6. Band-It was ordered to pay costs here and below, subject to the orders recorded. The question whether it could rely on a defence under section 62(1) of the Patents Act 1977 was referred to the judge or master conducting the inquiry or account.

• Court of Appeal (Civil Division): Appeal allowed in [2002] EWCA Civ 465. The finding that claims 1 to 5 were invalid for obviousness was set aside.
• Patents County Court: Peter Prescott QC, sitting as a deputy judge, held claims 1 to 5 obvious and invalid, but found that the respondent's ties would infringe if the claims were valid.