To be successful in a claim you need to establish that the design in which design right subsists has been copied so as to produce “articles exactly or substantially to that design”. Mere similarity is not enough. It needs to be re-produced exactly or substantially.
In C& H Engineering v F Klucznik & Sons Ltd  FSR 421 Aldous J said:
“Under section 226 there will only be infringement if the design is copied so as to produce articles exactly or substantially to the design. Thus the test for infringement requires the alleged infringing article or articles be compared with the document or article embodying the design. Thereafter the court must decide whether copying took place and, if so, whether the alleged infringing article is made exactly to the design or substantially to that design. Whether or not the alleged infringing article is made substantially to the plaintiff’s design must be an objective test to be decided through the eyes of the person to whom the design is directed.”
Therefore focus on two criteria one, copying and two making articles exactly or substantially to the copied design. If copying is not established, then whether the article is the same or substantially the same as the protected design does not matter. However, similarity in design may allow an inference of copying to be drawn.
The House of Lords in Designers Guild Ltd v Russell Williams 2000 1 WLR 2416 considered the question of copying in relation to an artistic work:
“The first step in an action for infringement of artistic copyright is to identify those features of the defendant’s design which the plaintiff alleges have been copied from the copyright work. The court undertakes a visual comparison of the two designs, noting the similarities and the differences.
The purpose of the examination is not to see whether the overall appearance of the two designs is similar, but to judge whether the particular similarities relied on are sufficiently close, numerous or extensive to be more likely to be the result of copying than of coincidence.
It is at this stage that similarities may be disregarded because they are commonplace, unoriginal, or consist of general ideas.
If the plaintiff demonstrates sufficient similarity, not in the works as a whole but in the features which he alleges have been copied, and establishes that the defendant had prior access to the copyright work, the burden passes to the defendant to satisfy the judge that, despite the similarities, they did not result from copying.
Even at this stage, therefore, the inquiry is directed to the similarities rather than the differences. This is not to say that the differences are unimportant. They may indicate an independent source and so rebut any inference of copying.
But differences in the overall appearance of the two works due to the presence of features of the defendant’s work about which no complaint is made are not material. In the present case the disposition of the flowers and (except in one instance) the colourways of the defendant’s design are very different from those of the plaintiff’s design. They were not taken from the copyright work, and the plaintiffs make no complaint in respect of them.
They make a significant difference to the overall appearance of the design. But this is not material where the complaint is of infringement of copyright and not passing off.”
Mummery LJ issued a note of caution in Farmers Build (at 481 and 482):
“Substantial similarity of design might well give rise to a suspicion and an allegation of copying in cases where substantial similarity was often not the result of copying but an inevitable consequence of the functional nature of the design. Copying may be inferred from proof of access to the protected work, coupled with substantial similarity. This may lead to unfounded infringement claims in the case of functional works, which are usually bound to be substantially similar to one another. The court must not forget that, in the field of designs of functional articles, one design may be very similar to, or even identical with, another design and yet not be a copy: it may be an original and independent shape and configuration coincidentally the same or similar.”
What is the role of an expert?
The expert needs to give a balanced view and not just point out the similarties.
In considering the question of copying the function of the experts is not to evaluate the factual evidence, but to point out to the court the similarities and differences between the design and the alleged infringement and the significance of those similarities and differences, so that the court can come to a view on whether they are such as to lead to a rebuttable inference that the defendant has copied the claimant’s design.