Attacking a Patent on lack of inventive step
If you are sued for patent infringement it will be necessary to attack the validity of the patent on the grounds that the patent is invalid. A patent shall be considered to be valid if it is taken to involve an inventive step if it is not obvious to a person skilled in the art having regard to any matter which forms part of the state of the art.
The leading cases concerning obviousness was referred to by the Court of Appeal in Windsurfing International Inc v Tabur Marine  RPC 59 and Pozzoli v BDMO. The tests as laid out in Pozzoli is as follows:-
(1) (a) Identify the notional person skilled in the art.
(b) Identify the relevant common general knowledge of that person.
(2) Identify the inventive concept of the claim in question or if that cannot readily be done, construe it.
(3) Identify what, if any, differences exist between the matter cited as forming part of the “state of the art” and the inventive concept of the claim or the claim as construed.
(4) Viewed without any knowledge of the alleged invention as claimed, do those differences constitute steps which would have been obvious to the person skilled in the art or do they require any degree of invention?
Attacking any patent is a risky and expensive thing to do. It is also fraught with risk for the patent holder as many patents are revoked once challenged. You will often find the following in any Judgement ” I find that the patent has been infringed but is invalid”.