Patents – Defences to Infringement

Main defences

Defences to patent infringement are outlined in the Patents Act 1977 (PA 1977). Under s 60(5), actions which would normally infringe a patent for an invention will not do so if it:

  • is done in private and for non-commercial purposes;
  • is done for experimental purposes relating to the subject-matter of the invention;
  • relates to a use that is exclusively for the needs of a ship or aircraft as long as the vessel is only temporarily in UK territorial waters or airspace (this is to allow ships or aircraft seeking repairs to find a safe port/ airport without infringing a patent for importing a specific part);
  • involves the preparation of medicine in a pharmacy for someone in accordance with a prescription given by a registered medical or dental practitioner or dealing with a medicine so prepared;
  • involves a patent owner selling a farmer a patented product that will then create a crop and the farmer uses the results of that crop to seed another crop on his own land. This also applies if the farmer was sold an animal that then reproduces.


Instead of arguing a defence, it is sometimes preferable to argue that the patent that you have infringed is invalid. In this case there can be no infringement as the patent should never have stood in the first place. When using this defence under s 74(1) of PA 1977, it may not be that the whole of the patent is declared invalid. It is possible to get only part of the patent declared invalid, thus creating a loop-hole in the patent into which your use of the invention falls.

Prior use

Under s 64(1) of PA 1977, if A was using the invention before the priority date but not publicly (eg, where a manufacturing technique was used by company A in an area subject to trade secrets and later patented by company B), A may be allowed to continue using the invention but only in the manner in which they had used before the priority date of the patent.
This is a personal defence which cannot be transferred. Only the person (natural or legal) who was using the invention prior to the priority date may use this defence and the rights cannot be sold. There is also a requirement that the ‘infringing act’ be done in good faith.


Showing you have a valid licence is a legitimate defence: the patent owner will have given you permission to carry out the act in the licence and as there is permission there can be no infringement. While this may seem clear cut, the way the contract is written may lead to differing interpretations of which acts the licensee may actually carry out.

Gillette defence

The Gillette defence is an extension of showing the patent you allegedly infringe is invalid. If you can show your product/process is wholly covered by a piece of prior art, it cannot infringe the patent for the new invention. The reasoning here is that you are basically using a product/ process known at the time of the patent (ie, you are recreating prior art) and if your product/process is covered by the patent, the patent is invalid on the grounds of novelty.


If you have been found guilty of patent infringement the courts can order:

  • an injunction – to stop you infringing further
  • ‘delivery-up’ – to force you to hand over all infringing articles
  • account of profits – requiring you to hand over any profit you made from the infringement;
  • damages – to compensate the patent holder for the loss they suffered due to your infringement
  • costs – forcing you to pay for your opponent’s legal fees
  • a certificate of contested validity – which allows a patent holder to show the validity of their patent has been attacked in the past and that attack failed.
Article written by...
Nicola Laver LLB
Nicola Laver LLB

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A non-practising solicitor, Nicola is also a fully qualified journalist. For the past 20 years, she has worked as a legal journalist, editor and author.