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How patent claims work: A variety of different AND statements, all OR’d together

The patent-infringement lawsuit against Facebook by Cross Atlantic Capital Partners (also known as XACP) is noteworthy in part because the patent has apparently survived reexamination by the Patent and Trademark Office. It will be interesting to see the final wording of the claims of the patent, and whether the patent owner had to amend any of the claims during the reexamination proceedings.

The claims of a patent are what determine infringement

People sometimes get all worked up about the fact that a patent describes X or Y or Z from the prior art. What matters for infringement purposes, however, is not so much what the patent describes, as what it claims. In the patent lawsuit against Facebook, just as in all such lawsuits, the exact wording of the patent claims will be crucial.

Each claim in a patent is a separate AND statement

Most patents have multiple claims. For a given claim to be infringed, all the elements of that claim must be present in the accused product or method, either literally or in the form of an “equivalent.”

Here are a couple of canonical hypothetical examples (simplified — they do not address the doctrine of equivalents), and pseudocode for their AND-statement equivalents. In these examples, a three-legged stool would infringe claim 1, but it would not infringe claim 5.

Claim 1: A seating structure comprising a seating platform and at least three legs.

  • IF (seating platform == TRUE) AND (no. of legs ≥ 3) THEN (infringement of claim 1 = TRUE)
  • IF (seating platform == TRUE) AND (no. of legs ≥ 3) AND (decorations == bunnies) THEN (infringement of claim 1 = TRUE)
  • IF (seating platform == FALSE) AND (no. of legs ≥ 3 ) THEN (infringement of claim 1 = FALSE)
  • IF (seating platform == TRUE) AND (no. of legs < 3 ) THEN (infringement of claim 1 = FALSE)

Claim 5: A chair comprising a seating platform and four legs.

  • IF (seating platform == TRUE) AND (no. of legs ≥ 4) THEN (infringement of claim 5 = TRUE)
  • IF (seating platform == TRUE) AND (no. of legs ≥ 4) AND (hasBackSupport == TRUE) AND (hasFootRest == TRUE) THEN (infringement of claim 1 = TRUE)
  • IF (seating platform == TRUE) AND (no. of legs < 4) AND (hasBackSupport == TRUE) AND (hasFootRest == TRUE) THEN (infringement of claim 1 = FALSE)

You can also think of each individual claim in a patent as being a separate infringement checklist: At trial, the patent owner’s lawyers and expert witness(es) will methodically talk the jury through that claim (and probably others as well), putting on evidence to show that every claim element is present in what the defendant is doing.

Claim interpretation is often a big deal

Very often, patent owners and accused infringers engage in expensive legal battles over “claim construction,” that is, the proper interpretation of different words and phrases in a patent claim. In the examples above, such a battle might break out over whether the term “seating platform” encompasses a camp chair with a soft, foldable cloth seat.

As a general rule, a given word or phrase in a claim will be interpreted in light of con­sid­er­a­tions such as the following:

  • the ordinary meaning of the term in the relevant art(s);
  • any special meaning stated by the inventor in the patent’s written description — the inventor is free to be his own lexicographer;
  • how the term was used in the back-and-forth correspondence between the inventor and the patent examiner, referred to as the ‘pros­ec­u­tion history’ of the patent application;
  • whether a particular meaning is required — other things being equal, a narrower interpretation that will preserve the patentability of the claim will be preferred over a broader interpretation that would result in the claim being invalidated by prior art. (If this issue comes up during the prosecution of the patent application, the patent examiner is supposed to require the applicant to amend the claim to eliminate the ambiguity.)

Only one claim need be proved infringed

As long as the patent owner proves that at least one claim is infringed, and the de­fend­ant doesn’t prove that the infringed claim(s) are invalid, then the defendant is liable for infringement.

Suppose hypothetically that the example claims above were actually in an unexpired patent, and that they were not proved to be invalid.

In that case, anyone who made, used, sold, offered for sale, or imported a three-legged stool would be liable for infringement, even though the stool infringed only claim 5 and not claim 1.

(Hat tip: George Grellas via Hacker News.)

(UPDATE: See also this post on the basics of patent validity analysis.)

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