Patent validity: The claims’ AND statements cannot return TRUE when applied to prior art

More on the patent-infringement lawsuit by Cross Atlantic Capital Partners (also known as XACP) against Facebook:

As discussed in a previous post on patent infringement, you can think of an individual patent claim as an AND statement. If all the elements of that claim are present in a (single) piece of prior art — that is, if the AND statement of a given claim returns TRUE when applied to that prior art — then that claim is invalid.

Or, putting it another way, if a claim is ‘infringed’ by a (single) piece of prior art, then that claim is unpatentable to that particular inventor.

(If a claim is not ‘infringed’ by a single piece of prior art, but it is ‘infringed’ by a combination of prior art, then the more-complicated obviousness analysis has to be applied.)

Here again are the hypothetical claims discussed in the previous post:

• Claim 1: A seating structure comprising a seating platform and at least three legs.
• Claim 5: A chair comprising a seating platform and four legs.

Both of these hypothetical claims could easily be proved invalid, because it’d be easy to show that both four-legged chairs and three-legged stools have been around for centuries.

A patent infringer can escape liability if it can prove that all infringed claims are invalid. (The proof must be by clear and convincing evidence, but that’s a topic for another post.)