Optis Cellular Technology LLC & Ors v Apple Retail U.K. Limited & Ors

In an appeal on patent obviousness, the claimed invention must be assessed as a whole and with care against hindsight. A logical sequence of routine steps reconstructed after the invention is known does not necessarily establish obviousness. Construction of a technical document is for the court. Expert evidence assists on technology, common general knowledge and the skilled person’s likely response, but does not determine the document’s meaning.

Where a reference work clearly warns against using a particular mathematical method, the court must not treat that warning as confined to demanding applications without sufficient evidential basis. Here, the relevant reference taught away from using a linear congruential generator alone. The claim was therefore not obvious and the revocation order was set aside.

Optis appealed from an order of Meade J revoking three European Patents (UK), following the third technical trial in a dispute concerning a FRAND licence of allegedly standard-essential patents. The order was made for the reasons given in [2021] EWHC 3121 (Pat).

Apple accepted that the principal patent was essential to the LTE 4G standard and would be infringed if valid. The trial judge held claims 1 and 4 obvious over Ericsson, a presentation concerning PDCCH blind decoding. Claim 1 used a linear congruential generator and a modulo operation to determine search-space positions. Claim 4 specified particular generator parameters. The appeal challenged the trial judge’s treatment of hashing functions, random number generators, the literature, and the warnings against linear congruential generators in NRC3. The central issue was whether the route from Ericsson to the claimed method was obvious without hindsight.

Majority decision. Arnold LJ gave the leading judgment and Nugee LJ agreed with him on the decisive ground. Birss LJ dissented on that ground and would have dismissed the appeal.

1. Obviousness is a multifactorial evaluation. An appellate court should not interfere with a first-instance conclusion unless there is an error of law or principle: Actavis Group PTC EHF v ICOS Corp [2019] UKSC 15, [2019] Bus LR 1318, and Re Sprintroom Ltd [2019] EWCA Civ 932, [2019] BCC 1031.
2. Expert evidence primarily educates the court about the relevant technology. The court must distinguish an expert’s assessment as a witness or teacher from the reasons for the expert’s opinion, which must be tested against what the notional skilled person would understand. Construction of a technical document is for the court; expert evidence may assist with the skilled person’s attributes, common general knowledge and likely response after reading it.
3. Grounds 1, 3 and 4 failed. Hashing functions and random number generators were conceptually related through randomisation, although they remained different techniques. The trial judge was entitled to find that the skilled person would retain the modulo operation, which performed the necessary range-mapping function, and investigate an established randomisation method, including an RNG.
4. Ground 5 succeeded. NRC3’s clear primary message was that a generator based principally on an LCG should not be used alone. Its qualification concerning carefully controlled situations did not confine the warning to demanding applications. The trial judge had elided construction of NRC3 with the separate question of what the skilled person would do after reading it. There was no sufficient basis in NRC3, Knuth or the common general knowledge for ignoring the warning. NRC3 therefore taught away from the claimed use of an LCG, and claim 1 was not obvious over Ericsson.
5. The sequential nature of the trial judge’s analysis also supported the majority’s concern about hindsight. Although a step-by-step route may establish obviousness where it is not hindsight-driven, the route here was reconstructed after the utility of the mathematical method was known. It was unnecessary to decide ground 7a in detail. The appeal was allowed and the revocation of the patents in suit was set aside.
6. Birss LJ considered that the trial judge was entitled to assess NRC3 and Knuth together, accept the expert evidence that the application was less demanding than those addressed by NRC3, and conclude that an LCG was suitable. In his view the step-by-step reasoning was supported by evidence and involved no improper hindsight.

1. Court of Appeal (Civil Division) allowed the appeal and set aside the revocation of the patents in suit: [2023] EWCA Civ 438.
2. High Court of Justice, Patents Court Meade J revoked European Patents (UK) Nos. 2 093 953, 2 464 065 and 2 592 779 by order dated 10 December 2021, for reasons given in [2021] EWHC 3121 (Pat).