You cannot develop a reputation for somebody who gives up. You have to be known as a fighter for your rights. Otherwise, you'll never license anything...Even Thomas Edison had a tough time supporting and protecting his patents. He spent about $1.4 million [to defend his inventions], and this was around the turn of the century, when beer was a nickel. - Jerome H. Lemelson, Named inventor on over 600 patents.

A product accused of infringing a patent can do so either literally or under the doctrine of equivalents. Literal infringement occurs when the accused product contains every limitation set forth in the claim at issue. A product infringes under the doctrine of equivalents when every limitation in the claim is literally present or when only “insubstantial differences” distinguish the missing limitation and the corresponding feature of the accused product. Essentially, if a device performs substantially the same function in substantially the same way to obtain substantially the same result, then infringement by equivalency may be found.

The infringement analysis is a two-step inquiry. First, the Court must determine the scope and meaning of the claim(s) at issue as a matter of law . Second, the finder of fact must compare the accused product to the properly construed claim to determine whether there has been an infringement. The patent holder bears the burden of proof by a preponderance of the evidence that each of the claim's limitations are found either literally or equivalently in the accused product. Each element of a claim is material and essential. In order for a court to find infringement, the plaintiff must show the presence of every element or its substantial equivalent in the accused device. If the accused product lacks one or more of the claim's limitations, either literally or equivalently, the product cannot infringe.

The Claim Interpretation Process

To ascertain the meaning of claims, the Court has developed a set of claim construction rules. The Court looks to the intrinsic evidence of record, the claims, the specification, and the prosecution history. If the meaning of the claim can be ascertained through an analysis of the intrinsic evidence, “it is improper to rely on extrinsic evidence.” (e.g. expert testimony).

First, the Court looks to the language of the claim itself. Words in claims generally are given their ordinary and customary meaning unless a different meaning is expressly set forth in the patent and file history.

Second, the Court looks to the specification. “Claims must be read in view of the specification.” The specification is usually the best guide to the meaning of a disputed term.

Third, the Court must also consider the prosecution history. Arguments and amendments made during the prosecution of a patent application and other aspects of the prosecution history, as well as the specification and other claims must be examined to determine the meaning of terms in the claims. The prosecution history limits the interpretation of claim terms so as to exclude any interpretation that was disclaimed during prosecution. Claims may not be construed one way in order to obtain their allowance and in a different way against accused infringers. Any interpretation provided or disavowed in the prosecution history defines the scope of the claim. Thus, the doctrine of prosecution history estoppel bars a patentee from asserting that a claim amendment made during prosecution for reasons of patentability encompasses limitations that were surrendered during the prosecution of the patent.

Who May Infringe

Whoever without authority makes, uses, offers to sell, or sells any patented invention, within the United States, or imports into the United States any patented invention, during the term of the patent infringes the patent. In addition, whoever actively induces infringement of a patent shall be liable as an infringer. Furthermore, a party can be held liable of “contributory infringement”, which is the act of knowingly selling a non-staple article specially made or adapted for use as part of a patented invention. To constitute a “non-staple” the article must not be suitable for substantial use in any other way than to infringe the patent.

Defenses to Infringement

The alleged infringer may assert as a defense that there is no infringement, that the patent is invalid for technical reasons, or is unenforceable due to inequitable conduct during prosecution of the patent.

Non-infringement

As discussed above, the Court must interpret the claims that are allegedly infringed. Once the claims have been properly construed, the finder of fact will compare the properly construed claims to determine whether each and every element of the claims at issue is contained in the accused device either literally or equivalently. If not, there is no infringement.

Invalidity

An invention must be (1) “novel,” (2) “useful”, (3) different from the prior art or “non-obvious.” An issued patent is presumed to be valid as a matter of law. That presumption is overcome, however, if the patent is shown to lack any one of those requirements, and the patent then will be held invalid.

Anticipation and Obviousness

Invalidity by lack of “novelty” or anticipation results if each and every element of the claimed invention appears in a single reference published more than one year before the filing date of the patent. The reference need not recite word for word what is in the claims, it is anticipatory if the claimed element or limitation is “inherent” or otherwise implicit in the reference. Whereas anticipation requires that the claimed invention must appear in a single reference, obviousness occurs where the claimed invention is found in two or more references and a person of ordinary skill in the art would have known to combine those references to achieve the invention. In either case, the patent will be held invalid.