I. What is the "doctrine of equivalents"?

Patent infringement is ordinarily understood to mean as the unauthorized replication or use of a patented invention or process. Technically, however, patent infringement is committed either literally or by equivalents. Literal infringement exists when every limitation recited in a patent claim is found in the infringing device (or process). Infringement by equivalents, on the other hand, happens when a device (or process) appropriates a prior invention by incorporating its innovative concept and, although with some modification and change, performs substantially the same function in substantially the same way to achieve substantially the same result. This "function-way-result" equation lies at the heart of the doctrine of equivalents.

The doctrine of equivalents is a common law concept borne out of American jurisprudence. It is an equitable measure to protect patentees against deliberate efforts of infringers to evade liability for infringement by making only insubstantial changes to a patented invention. In other words, it extends protection beyond the specific and literal claims of patents. In one of its recent decisions, the U.S Supreme Court restated the time-honored rationale behind the application of the doctrine of equivalents:

The language in the patent claims may not capture every nuance of the invention or describe with complete precision the range of its novelty. If patents were always interpreted by their literal terms, their value would be greatly diminished. Unimportant and insubstantial substitutes for certain elements could defeat the patent, and its value to inventors could be destroyed by simple acts of copying. For this reason, the clearest rule of patent interpretation, literalism, may conserve judicial resources but is not necessarily the most efficient rule. The scope of a patent is not limited to its literal terms but instead embraces all equivalents to the claims described. (Festo v. Shoketsu Kogyo Kabushiki Co. Ltd., 535 U.S. 722, 152 L. Ed. 2d 944. 122 S. Ct. 1831 [2002])



II. The Doctrine as Entrenched in American Jurisprudence

One of the earliest manifestations of the doctrine of equivalents in American jurisprudence was in Winans v. Denmead (15 How. 330, 347 [1854]). In Winans, the doctrine was expressed in this wise: "the exclusive right to the thing patented is not secured, if the public are at liberty to make substantial copies of it, varying its form or proportions."

Close to a century later, the debate over whether the doctrine of equivalents should be afforded a second look took center stage in Graver Tank & Mfg. Co. v. Linde Air Products Co. (339 U.S. 605 [1950]). Clearing the air of doubts on the matter, the Court in Graver Tank ruled that "patent claims must protect the inventor not only from those who produce devices falling within the literal claims of the patent but also from copyists who make unimportant and insubstantial changes and substitutions in the patent which, though adding nothing, would be enough to take the copied matter outside the claim, and hence outside the reach of law."

Recently, the doctrine's stronghold as an important consideration in patent infringement determination was reaffirmed in Warner-Jenkinson Co. v. Hilton Davis Chemical Co. (520 U.S. 17 [1997]). Warner-Jenkinson held that:

If the essential predicate of the doctrine of equivalents is the notion of identity between a patented invention and its equivalent, there is no basis for treating an infringing equivalent any differently than a device that infringes the express terms of the patent.

While the doctrine of equivalents is firmly entrenched in American jurisprudence, its applicability is nonetheless subject to limitations i.e. existence of prior art, technological advances and prosecution history estoppel. These limitations had been subjects of numerous cases decided by the U.S. Court of Appeals Federal Circuit and the U.S. Supreme Court, some of the most significant of which are the so-called "Festo" rulings on the scope and extent of prosecution history estoppel as a limitation to the applicability of the doctrine of equivalents (please see related article entitled "Prosecution History Estoppel: Festo I and II Revisited").



III. Doctrine of Equivalents: Finding its niche in Philippine jurisprudence.

In the Philippines, the doctrine of equivalents finds statutory basis in Section 75.2 of R.A. No. 8293, otherwise known as the Intellectual Property Code ("IP Code"), which states:

For the purpose of determining the extent of protection conferred by the patent, due account shall be taken of elements which are equivalent to the elements expressed in the claims, so that a claim shall be considered to cover not only all the elements as expressed, but also equivalents.

However, in as far as Philippine jurisprudence is concerned, discussion on the doctrine of equivalents is relatively scarce. In fact, only three cases delved on the subject of equivalents vis-a-vis patent infringement. Surprisingly, the earliest mention of the doctrine was in Carlos Gsell v. Valeriano Veloso Yap-Jue (G.R. No. 4720, January 19, 1909) where there was no substantial discourse on the matter but merely a token reference to an American case.

In Pascual Godines v. Court of Appeals, et al. (G.R. No. 97343, September 13, 1993), the Supreme Court relied on the doctrine of equivalents when it found patent infringement against an individual for manufacturing and selling "power tillers" in substantially the same mold as that of a patented model. In Pascual Godines, the doctrine as conceived and defined in American jurisprudence, was re-stated, thus:

Recognizing that the logical fallback position of one in the place of defendant is to aver that his product is different from the patented one, courts have adopted the doctrine of equivalents which recognizes that minor modifications in a patented invention are sufficient to put the item beyond the scope of literal infringement. Thus, according to this doctrine, "(a)n infringement also occurs when a device appropriates a prior invention by incorporating its innovative concept and, albeit with some modification and change, performs substantially the same function in substantially the same way to achieve substantially the same result." The reason for the doctrine of equivalents is that to permit the imitation of a patented invention which does not copy any literal detail would be to convert the protection of the patent grant into a hollow and useless thing. Such imitation would leave room for - indeed encourage - the unscrupulous copyist to make unimportant and insubstantial changes and substitutions in the patent which, though adding nothing, would be enough to take the copied matter outside the claim, and hence outside the reach of the law.

More recently, in Smith Kline Beckman Corp. v. Court of Appeals, et al. (G.R. No. 126627, August 14, 2003), the Supreme Court struck down a patent infringement suit because the petitioner fell short of substantiating the function-means-and-result requirement for infringement by equivalents. It nevertheless reiterated its recognition of the doctrine of equivalents in Pascual Godines:

The doctrine of equivalents provides that an infringement also takes place when a device appropriates a prior invention by incorporating its innovative concept and, although with some modification and change, performs substantially the same function in substantially the same way to achieve substantially the same result.

While the doctrine of equivalents is recognized in Philippine jurisprudence, the High Court has yet to render an incisive discussion on the matter. Other than reference to the vast sources of American case law on the doctrine, Philippine jurisprudence offers no hint as to the extent of its applicability. As to how the Supreme Court would eventually appreciate the scope of prosecution history estoppel, for instance, remains to be seen. Would the Supreme Court regard prosecution history estoppel as a complete bar to the applicability of the doctrine of equivalents? Alternatively, would the Court provide some leeway for patentees to refute estoppel?

At present, there may be very few cases dealing with prosecution history estoppel that are pending with the Intellectual Property Office. However, until these cases actually reach the Supreme Court and are resolved with finality, patent infringement litigants will have to rely exclusively on American authorities for applicable case law on the matter.