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Scope of protection: around and around the numbers

21 July 2015

In the recent case of Smith & Nephew Plc v ConvaTec Technologies Inc (see here), the Court of Appeal issued an interesting decision concerning how the boundaries of a range in a claim should be interpreted. In a surprise move, they concluded that a claimed range of “between 1{e27634494e39db391c4a3c1babcce9c96667e0da0c02f00a98e80c871bbff07c} and 25{e27634494e39db391c4a3c1babcce9c96667e0da0c02f00a98e80c871bbff07c}” of an agent should be interpreted to cover down to 0.5{e27634494e39db391c4a3c1babcce9c96667e0da0c02f00a98e80c871bbff07c}.

ConvaTec own a patent with claims to a method of making a material for wound dressings. The claim in question has three steps, the third of which recites using an agent present in a concentration of “between 1{e27634494e39db391c4a3c1babcce9c96667e0da0c02f00a98e80c871bbff07c} and 25{e27634494e39db391c4a3c1babcce9c96667e0da0c02f00a98e80c871bbff07c}”. Smith & Nephew Plc make their own range of wound dressings using 0.77{e27634494e39db391c4a3c1babcce9c96667e0da0c02f00a98e80c871bbff07c} of the agent. The question, therefore, was whether or not 0.77{e27634494e39db391c4a3c1babcce9c96667e0da0c02f00a98e80c871bbff07c} is covered by the claimed range.

ConvaTec argued that the skilled person would assume that the numbers in the range have been subject to rounding to the nearest whole number. The lower limit would therefore be 0.5{e27634494e39db391c4a3c1babcce9c96667e0da0c02f00a98e80c871bbff07c}, meaning that Smith & Nephew infringe their claim.

Smith & Nephew argued that the limits of 1{e27634494e39db391c4a3c1babcce9c96667e0da0c02f00a98e80c871bbff07c} and 25{e27634494e39db391c4a3c1babcce9c96667e0da0c02f00a98e80c871bbff07c} are absolute, and anything falling outside these limits does not infringe the claim.

To determine whether or not Smith & Nephew’s product falls within the scope of the claim, the court asked: would the skilled person assume that the patentee had intended for the boundary of the claimed range to be rounded to a certain degree of accuracy, and, if so, which rounding convention would they have used?

At first instance, in the High Court trial, Judge Birss ruled that the skilled person would consider the numbers to have been rounded to the nearest significant figure. Using this rounding, the claim covers the agent at a concentration of 0.95{e27634494e39db391c4a3c1babcce9c96667e0da0c02f00a98e80c871bbff07c}-25.5{e27634494e39db391c4a3c1babcce9c96667e0da0c02f00a98e80c871bbff07c}, and hence the Smith & Nephew product would not infringe.

On Appeal, the Court of Appeal overturned this decision, and concluded that the skilled person would consider the numbers to have been rounded to the nearest whole number. Under this decision, the claim covers the agent at a concentration of 0.5{e27634494e39db391c4a3c1babcce9c96667e0da0c02f00a98e80c871bbff07c}-25.5{e27634494e39db391c4a3c1babcce9c96667e0da0c02f00a98e80c871bbff07c}, and so the Smith & Nephew product would infringe.

In the Court of Appeal decision, Judge Kitchin refers to a number of reasons for the ruling. Numbers in the description of the patent in question are expressed to a varying degree of precision (some to 0 decimal places, others to 1 decimal place). Judge Kitchin concluded that this demonstrated that the patentee could express numbers to a high degree of precision, and lead him to believe that the “skilled person would understand that the patentee has chosen to express the numerical limits of the range in the claim to only a limited degree of accuracy”.

Further, the description states that the method would work with an agent concentration of between 0.01{e27634494e39db391c4a3c1babcce9c96667e0da0c02f00a98e80c871bbff07c} and 50{e27634494e39db391c4a3c1babcce9c96667e0da0c02f00a98e80c871bbff07c}. The Judge found that this would teach the skilled person that there is no technical reason that the numbers in the claim should be absolute.

It may also be that the asymmetrical latitude afforded by the significant figure rounding in Judge Birss’ decision (0.05{e27634494e39db391c4a3c1babcce9c96667e0da0c02f00a98e80c871bbff07c} at the bottom of the range, and 0.5{e27634494e39db391c4a3c1babcce9c96667e0da0c02f00a98e80c871bbff07c} at the top) was unappealing to the Court of Appeal.

Many people believe that this Court of Appeal decision is too generous in favour of the patentee. A criticism that has been levelled is that the court looked at the claim through the eyes of a mathematician, rather than a chemist and that a chemist would use margins of error rather than whole number rounding. Under the Court of Appeal decision the claim allows for a 50{e27634494e39db391c4a3c1babcce9c96667e0da0c02f00a98e80c871bbff07c} margin of error, which would be unacceptable to a chemist.

This decision contrasts with two other High Court decisions, FNM Corporation Ltd v Drammock International and Halliburton Energy Services Inc v Smith International (North Sea) Ltd, in which the court interpreted the scope of the claims using the significant figure rounding convention. It will be interesting to see whether the whole number rounding approach will now be taken as standard in other cases, or whether the degree of accuracy will be decided on a case by case basis.
Emily Collins and Elizabeth Swan
Electronics, Computing & Physics and Life Sciences & Chemistry

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This publication is a general summary of the law. It should not replace legal advice tailored to your specific circumstances.

© Withers & Rogers LLP, July 2015