Patents – Defences to Infringement

The main defences

Defences to patent infringement are given under section 60(5) of the Patents Act 1977. This provides a list of situations under which an act that would otherwise be infringement does not actually commit an infringement 

  • Private Use – If the infringing act is done in private and for non-commercial purposes there is no infringement.

  • Experimentation – In general, if the patented item is used to experiment in a non-commercial manner it will be covered by an exception to infringement. For example, if the infringing act is done for experimental purposes relating to the technological area of the invention then there is no infringement. This would be the case if, for example, an older invention was being experimented upon to find new improvements. If, however, a university uses the patented item in an experiment they may find themselves subject to an infringement case if they then turn their research into a product as it would then become commercial.

  • Ships and Aircraft – If the infringing act relates to a use that is exclusively for the needs of a ship or aircraft there is no infringement as long as the ship or aircraft is only temporarily in UK territorial waters. This is to allow aircraft and ships seeking repairs to find a safe port or airport without then finding themselves infringing a patent for importing a specific part. 

  • Pharmacies – the preparation of medicine in a pharmacy for an individual is not patent infringement even tough it may be seen as a ‘disposing’. This could be the case when dealing with patented drugs. 

  • Farmers – where a patent owner has sold a farmer a patented product that will then create a crop, he may not then sue for infringement if the farmer uses the results of that crop to seed another crop on his own land. This also holds if the farmer was sold an animal that then reproduces.


Instead of arguing a defence, it is sometimes preferable to instead 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. The law in this area is held under section 74(1) of the Patents Act 1977. When using this method of defence 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. 

The idea of proving a patent invalid often includes the party pursuing the invalidity showing that the subject of the patent was known before the priority date of the patent itself. This amounts to finding a piece of prior art that was not found at the time of the patent and showing that it was in the public domain thereby attacking the novelty of the patent. A successful attack in this manner is likely to either destroy or limit the patent to a point which it can be worked around.

Prior Use

Section 64(1) of the Patents Act 1977 gives the possibility that a person was using the invention before the priority date but not publicly. Such could be the case where a manufacturing technique was used by company A in an area subject to trade secrets and later patented by company B. In this situation company A would be allowed to continue using the invention but only in the manner in which they had used before the priority date of the patent (i.e. if they were making products they couldn’t be sued for the infringing act of making but may still possibly be sued for then selling the result).

This is a personal defence, meaning it 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.

The prior use defence can also be stretched to cover serious and effective preparations. This requires that the infringing party was so advanced in their actions that they are about to result in the infringing act. This is not a reliable extension to the defence, however, and would be difficult to prove.


Showing that you have a valid licence is a legitimate defence. This is basically saying that the patent owner has given you permission to carry out the act in the licence and as there is permission there can be no infringement. Whilst 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. There may also be complications if the patent has been sold by the original proprietor and full details of prior licence agreements have been poorly communicated.

Gillette Defence

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


If you have been found guilty of patent infringement there are a number of course the courts can take. Amongst others an injunction can be ordered to stop you from infringing further or ‘delivery-up’ can be ordered to force you to hand over all infringing articles. Monetary compensation can be ordered in different ways. Account of profits means you hand over any profit you made form infringing, Damages will judge the loss the patent holder suffered due to your infringement and compensate them and Costs can force you to pay for your opponent’s legal fees. It is also possible to be granted a certificate of contested validity, which allows you to show that the validity of your patent has been attacked in the past and that attack failed.