There are 7 main defences / exceptions to patent infringement claims. This article briefly outlines each of the possible defences.
1) Expiry – this is a simple defence and is merely showing that the period of protection for the patent has expired (i.e. it has not been renewed etc)
2) Invalidity – this is probably the most common form or defence and is a challenge to the validity of the patent and claims that the patent should be revoked (section 74). Where a court rules a patent to be valid, an owned can apply for a certificate of contested validity (section 65) this acts to discourage future contesting of the patent as the patentee will be entitled to costs in such an action. Should the patent be declared invalid then remedies will only be available to a patent owner for infringement of the valid (if any) part / parts and damages may not be available for all of the infringing acts
3) Limited scope of patent claims – it is also a defence to show that the patent claims do not actually cover the alleged offence(s)
4) Private, non-commercial use – showing that an invention was used privately and for non-commercial purposes is a defence under section 60(5)(a)
5) Experimental purposes – use of an invention for experimental purposes related to the subject matter of the invention is a defence under section 60(5)(b)
6) Innocent infringement – this is only a partial defence i.e. it prevents damages or account of damages being awarded if the defendant can show that they a) did not know or b) had no reasonable grounds for suspecting… that the patent existed
7) Previous use – where a party previously used an invention in the UK in good faith (prior to the patent application being filed) then the party can continue to use the invention despite the grant of the patent.