CL-2022-000676 - [2025] EWHC 2486 (Comm)

An essential part of the background to this case is the concept of sterility. On one level this is a sale of goods case, like many others. Goods were bought and delivered. The buyer claims they are not of satisfactory quality and seeks to get its money back. That is the way this case was originally pleaded. It was advanced on the basis of the following propositions, familiar in their outlines to all commercial lawyers:

But sterile gowns are not bulk grain cargoes. The experts are agreed that sterility cannot be adequately tested for and that in practical terms it is not useful to contract by reference to sterility per se, essentially because (i) sterility (freedom from/absence of any viable micro-organism) is an absolute state – Mr Atchia, Medpro’s expert says “there is no half way house” (ii) there is no sensible way of testing this without destroying the sterility of the item in question.

If sterility is an absolute state how does the market stipulate for and assess sterility? The experts are agreed that this is done by reference to something called a “Sterility Assurance Level” (“SAL”). SAL represents the “theoretical probability” of sterility in relation to each medical device, namely the theoretical probability of there being (or of detecting, which in practice comes to the same thing), after sterilisation, a viable micro-organism on the device. The reference to assurance is a logical concomitant of this – because the theoretical probability of a microorganism is so low, the confidence or assurance level can be high. The user can be in mathematical terms next door to sure that the item is sterile.

In this case it is common ground that the contractually stipulated SAL for the gowns was 10^-6.

That presents the question as to how SAL is achieved. That question is at least typically answered by a fairly complex web of standards. To understand even the factual background to this case and the outcome it is necessary to appreciate the following (some of which is repeated later in the judgment as relevant).

Any assessment of SAL is based on the demonstration of the absence of growth of any viable micro-organism following a sterility test. Industries that deal in questions of sterility will generally use official standards to set parameters for how this is to be done and what assurance level is needed. In the UK, for instance, these are standards published by the British Standards Institution and designated by the Government. Some of these standards may be non-British standards, for example, EU standards or International Standardisation Organisation (“ISO”) standards.

Some standards incorporate microbial inactivation data and have been developed to measure, control and demonstrate the efficiency of a sterilisation process. Some standards deal with other aspects of a process to reach the same goal – demonstration of the absence of growth of any viable micro-organism following a sterility test. Some standards deal with different ways of sterilising. In this case the method used was ionising radiation and the experts in this case agreed “ionising-radiation was a suitable- and perhaps the ideal - method to sterilise” medical gowns of the sort in question.