Doctrine Of Equivalence In UK Law
The recent case law from the House of Lords shows clearly that UK law and the European Patent Convention in practice (despite the theoretical denial) operate a doctrine of equivalence that is indistinguishable from that found in US law
The necessity of the doctrine of equivalence in contemporary patent law has long been a vexed one. Views may differ from country to country. Whilst some legal commentators in the United States consider the said doctrine to be indispensable, the enthusiasm is much less pronounced on the other side of the Atlantic, and more particularly in the United Kingdom. Critics of the doctrine posit that it has only aided to create uncertainty and unpredictability in IP by unreasonably increasing the scope of a patent in rather unpredictable ways.  Champions of the doctrine on the other hand insist that the protection a patent gives the inventor would be meaningless if the scope of the patent is construed to be so narrow that minor improvements to a device or tool are enough to bring the new product out of the scope of the original patent.  This essay will examine some of these claims, and shall specifically look at the application (or lack of it) of the doctrine across different jurisdictions.
Doctrine of Equivalents and the Scope of patents
The Doctrine of Equivalents, sometimes referred to as “DOE" is a remedy that has its basis in equity, and the underpinning of the doctrine is that there could be an infringement of a patent when a subsequent infringing device is deemed to be an equivalent to the claims of an existing patent.  A patent holder invoke the doctrine against a device (or a process in the case of process patents) if the device in question “if it performs substantially the same function in substantially the same way to obtain the same result".  Critics have pointed out that this jurisprudential theory may have the effect of extending a patent scope and turn its application to be “like a nose of wax, which may be turned and twisted in any direction, by
merely referring to the specification, so as to make it include something more than, or something different from, what its words express." 
The concept that a patent can be infringed by an equivalent device has been developing in the United States for about 150 years and there have been several decisions that have truly shaped that concept. The first case to reach the Supreme court in the US was Winans v. Denmead  and this was the first case that extended patent protection beyond the scope envisaged by the patent claims. The case involved a type of a rail road designed by Winan to carry some coal. Its form was cyrindrical and conical as opposed to being rectangular as was the norm then.
A competitor called Denmead came up with railroad cars that were octagonal and pyramid-like in shape, but the supposed advantages of this car were deemed as essentially the same as those of Winan. The Supreme Court found there had been an infringement as it would have been unreasonable to literally apply the content of the claims as the car was “so near to true circle as substantially to embody the patentee’s mode of operation and thereby attain the same kind of result as was reached by his invention."
That, plus several other elements formulated in other cases forms the raison d’être for the doctrine of equivalent. The doctrine is however not limited to the United States alone, but variations of it can be found in other jurisdictions as well rechristened and adopting a somewhat smaller scope than the one found in the Unites States. UK for instance recognized the doctrine and it was commonly referred to as the doctrine of pith and marrow. 
Whatever the name given to the concept of equivalents, it s emergence was not a historical accident but out of necessity. There was a desire to grant a patentee an adequate scope of protection as a trade-off for the disclosure of the specification. But there was also a desire to inform the public the limitations of a certain specification applicability so that members of the public can take steps to avoid infringement of that specification.
Protecting the patentee means just more than preventing others from copying the mechanism from a literal perspective. The imperfections of the language can severely limit a patent scope as language can sometimes be an imprecise vehicle to describe highly technical concepts.  This is something that many different jurisdictions, including US, UK and many Euro-zone countries recognize. 
The doctrine protects a patentee from an unscrupulous copyist who seeks to ran away with the most important aspect of an invention by making unsubstantial changes to it to circumvent the literal language used to describe a specification. Doctrine also protects the patentee from the unforeseen advances in technology. Many rush to file patent applications without appreciating the full potential scope and the significance of it until the commercialization of the said invention.  Therefore by allowing the patent holder to claim a wider scope of his invention, the pioneering inventor is rewarded in a manner commensuration to his contribution to the art.
The doctrine also serves a public interest. A patent holder is enabled to exclude every person from exploiting his device, and therefore it would be only fair to give the public a fair notice about the patentee claimed monopoly.  US law for instance requires the patentee to clearly define the scope of their patents, and by so doing, the public is encouraged to come up with the designs that are outside the scope of the existing patent using prior art technologies or coming up with completely new inventions in their own right.
If on the other hand the scope is deemed by many to be unclear, there is a danger that commerce will flounder if firms are unwilling to assume the risk of patent infringement in the general area related to an existing patent. This uncertainty may provide a disincentive to individuals and firms to conduct research and innovate in such areas unless they are willing to risk law suits as a result.
One of the greatest challenges courts and legislatures therefore face in patent law is to create rules for determining patent scope that maintain the protection a patent is meant to confer while still keeping the patent monopoly within reasonable bounds. Despite the general unity in patent laws among developed countries, the difficulty of this task has led to different results in different jurisdictions.
Many jurisdictions have chosen to determine patent scope under a doctrine of equivalents, while others have maintained the position that adequate scope can be found within the meaning of a patent’s claim. Even jurisdictions which agree that a doctrine of equivalents should apply differ significantly in its application as the following passages shall attempt to demonstrate.
Oh my Lord. The House of Lords and Patent law
Though traditionally reticent to accept patent cases, the House of Lords have in the recent years adjudicated over several patent cases that will have a big impact on the English patent law. English law clearly states that in order for a variant or an equivalent to infringe on a patent, it must be within the language of a claim. An equivalent that does not fall within the language of a claim, however much interpreted, cannot be infringing, despite the fact that such variant may amount to nothing more than an unfair copying of the very essence of the inventive concept.
Furthermore under English law and Article 69 of the European Patent Convention (EPC), which applies in the United Kingdom (U.K) finds that under the current English approach where the need to provide adequate notice of patent breadth to the public is balanced against fair protection to the patentee, a claim cannot be read literally, but is to be construed purposively in accordance with the specification and drawings.
Unlike in the United States, the U.K. approach to interpretations of patent claims is in fairly narrower terms. The U.K. referred to the doctrine of equivalents, as the doctrine of “pith and marrow"  under which, if the allegedly infringing device contains all of the elements of the claim, but some insubstantial elements are substituted with equivalent elements, then non-literal infringement of a patent is found.
To determine infringement, the U.K juries are specifically instructed to identify each of the essential features of the claimed invention in the accused invention and therefore infringement of every element and limitation is essential. The U.K. analysis of a patent infringement has barely survived the EPC provisions, but it was slightly modified.
Despite amending the language of the Protocol, the changes were not substantial enough to alter the law governing equivalents in the United Kingdom. After a decade of refusing to try any patent cases, the House of Lords (the highest court in the United Kingdom) heard and determined two important cases; Kirin Amgen v Hoechst Marion Rousell  and SABAF v MFI.  Both judgments were delivered in October 2004 with the former being substantially more important than the latter. In each case however the judgment was unanimous.
In the Sabaf v MFI the House of Lords maintained the structured test for obviousness (the Windsurfer test)  and applied it to a mere collocation of known and non-interacting features. In the Kirin-Amgen v Hoechst the House of Lords made some significant comments on the interpretation of claims in the UK. The previously common tests variously termed Improver or Protocol questions were not used and the interpretation of product-by-process claims in the UK was brought into conformity with that of the European Patent Office and a number of other European countries.
However in Kirin-Amgen v. Hoechst Marion Roussel Ltd., the ruling decision of the House of Lords, Lord Hoffmann was openly skeptical of the U.S. doctrine of equivalents remarking that “American patent litigants pay dearly for results which are no more just or predictable than could be achieved by simply reading the claims." Lord Hoffmann argued that giving claims a “purposive" construction eliminates any need for a doctrine of equivalents.
Kirin-Amgen v Hoechst Marion Roussel: A Brief discussion
Kirin-Amgen had invented a process for making the pharmaceutically active protein erythropoietin. They included claims to the protein per se in their patent which they claimed were infringed by Hoechst Marion Roussel Limited who manufactured erythropoietin albeit using a different process. The House of Lords have found the product claims invalid for insufficiency and anticipation.
Lord Hoffmann's opinion provides vital guidance on the Protocol Article 69 European Patent Convention (EPC)  and the interpretation of product-by-process claims in the UK.
The learned Judge point out that even through article 69 prevents equivalence from extending protection outside the claims; there should be no reason why it cannot be an important part of the background of facts known to the skilled man which would affect what he understood the claims to mean.
Hoffmann avoided referring to the Protocol as a guide in arriving at his decision saying that the in some instances the Protocol questions do not provide a solution. He was also of the opinion that the interpretation of claims in the U.K, Germany and the Netherlands is now not significantly different. Hoffmann has reversed the long-standing U.K approach to the interpretation of product-by-process claims and adopted the European Patent Office (EPO) approach that the claim is to the product per se with the process steps only limiting insofar as they relate to their effect on the product.
Recent United Kingdom cases have moved away from any doctrine of equivalents or similar interpretive tool, instead adopting a novel approach to claim interpretation that renders the doctrine of equivalents unnecessary.  Rather than focus on the literal meaning of the words in the claims, the House of Lords, in cases like in the fore mentioned Kirin-Amgen case, chose to alternatively focus on the meaning of the words to a person reasonably skilled in the art. In conjunction with this new interpretation standard, U.K. courts have ceased using the doctrine of equivalents to supplement claim interpretation in order to avoid the unpredictability and other social costs associated with broader claim interpretation. 
In LB Europe Ltd. v. Smurfit Bag in Box SA  , High Court of England and Wales it was held that "Once the monopoly has been allowed to escape from the terms of the claims, it is not easy to know where its limits should be drawn."
They argue that this new standard of interpretation eliminates the need for a claim-broadening device like the doctrine of equivalents because it puts the focus on the patentee's intent when he drafted the patent claims.  This should enable the patentee to draft better claims, aid all affected parties to better predict what the scope of the claims will be before they even reach a court. With U.S. cases like Phillips that address claim interpretation by adopting the same "reasonable person skilled in the art" standard created by the House of Lords in Kirin-Amgen, U.S. courts have taken a step toward abolishing the doctrine of equivalents. 
On its face, the purposive construction theory seems quite easy and straight forward, a quality other theories governing immaterial equivalents do not have. However, as noted earlier, its key limitation lies in the fact that it cannot protect an equivalent or variant that lies beyond the language of the claims. As to whether this is good or bad policy is a moot issue. Some may argue, as Lord Hoffman did, that it provides more clarity and is less expensive for litigants than the American doctrine of equivalents. However as regards fair protection to the patentee, it goes without saying that the patentee ought to be should the offending device in some way be supported by the specification.
As things stand however, the U.K legal system will only protect those variants that fall within the language of a claim. In this regard the EPC 2000 is unlikely to have a resounding impact or change anything, in so far as the English courts are concerned. However eventually if read in a manner that allows an extension of the scope of a patent to cover variants outside the language of a claim similar to the practice in the U.S, then the courts of law need to come up with a way to help intergrate this meaningfully.
Otherwise, the U.K courts may find themselves exhibiting the same anxiety as that once exhibited by the U.S. courts who had even gone on to lament in the Supreme Court decision of Warner-Jenkinson Co. v. Hilton Davis Chemical Co.  Here the court lamented the fact that the doctrine of equivalents had “taken on a life of its own, unbounded by the patent claims."
Currently we have no option but to wait and see how the tricky issue of equivalents is likely to play out in the U.K. Meanwhile, the jury is still out as to which country has the right solution in this regard. An appropriate balance of fair protection to the patentee with adequate notice of patent breadth to third parties seems to have be secured in the U.K law.
Equivalents in the United States
As already alluded to at the start of this discussion the doctrine of equivalents in the United States provides that the scope of a patent claim can extend beyond the literal words of the claim so that a device containing elements which though minor and/or insubstantial changes are equivalent to that claimed and may infringe the patent. 
The United States patent laws are found in Title 35 of the United States Code and more specifically under Section 271 of the same which deals with infringement.
Despite this, a careful analysis shows that the doctrine of equivalents is actually a fruit borne of the case law tree and not statute because Section 271 when studied carefully actually shows that it only codifies the statute on literal infringement.
The doctrine of equivalents has its roots in the United States Supreme Court decision in Winans v. Denmead.  The patent in this case described a railcar with a conical cavity for carrying coal, resulting in an even weight distribution of coal in the car and a lower center of gravity. The accused railroad car had octagonal
and pyramidal cavities instead, thus providing the same result as the plaintiff’s railcar without falling within the literal language of the [plaintiff’s patent. The trial court found no infringement. However but dissenting judges of Supreme Court found infringement, applying the following logic:
The rule of law for determining equivalency as laid down by the Supreme Court is quite simple:
"If two devices do the same work in substantially the same way, and accomplish substantially the same result, they are the same, even though they differ in name, form, or shape."
Despite the simplicity of this rule, its application to a particular case is often complex. Conflicting opinions of experts and disputes as to scientific or engineering facts are usually the route to arrive at a decision since what is deemed equivalent for one purpose may not be for the next.
It is noteworthy that the exclusive right to the device protected by patent is not secured if third parties are at liberty to make substantial copies of it, thus modifying its form or proportions. Consequently the patentee, having described his invention, and shown its principles, and claimed it in that form which most perfectly embodies it, is, in as per of law, considered to be protected.
Europe and the Doctrine of Equivalents: A brief comparative study.
Patent protection in many Eurozone countries is largely governed by Article 69 of the European Patent Convention (EPC).  This essay shall examine if there is any role the doctrine of equivalent plays in Europe patent law, and instead of commenting on each of the 27 contracting states regimes, the article will restrict itself to the doctrine applicability in Germany, Europe’s most important economy.
How does Europe deal with patent infringement, especially when the wording of the infringing device does not tally with the wordings of the existing patent? In Germany as well as other European nations, there is a broad consensus that patent infringement is not necessarily excluded and that the scope of an embodiment may extend beyond the wording in the claim.  The interpretation for the ECP is provided by the Protocol on interpretation and it inter alia provides as follows regarding article 69 of the convention;
“Article 69 should not be interpreted in the sense that the extent of the protection conferred by a European Patent is to be understood as that defined by the strict literal meaning of the wording used in the claim, the description and drawings being employed only for the purpose of resolving an ambiguity found in the claims. Neither should it be interpreted in the sense that the claims serve only as a guideline and that the actual protection conferred may extend to what from a consideration of the description and drawings by a person skilled in the art, the patentee has contemplated. On the contrary, it is to be interpreted as defining a position between these extremes which combines a fair protection for the patentee with a reasonable degree of certainty for third parties."
Initially, Germany attitude towards infringement learns towards patent infringement largely reflected the US position because it acknowledged that any device that envisaged the same inventive concept as an existing embodiment infringed the existing patent. 
It is commonly recognized as a principle that in any determination of infringement under the doctrine of equivalents, such should be done on an element by element basis so that it is infringement if it embodies each claim element or its equivalent. The principle is so well that such analysis proceeds directly to application of the doctrine of equivalents to those elements that do not fall within the literal language of the claim. Many countries follow the lead of others in developing their law.
The E.U. adopted the European Patent Convention (EPC) which sets out common rules of patent interpretation and although E.U. have members held differing opinions on the scope of patent claims, the members decisions usually refer to the common rules of interpretation and it is these rules that support their decisions. In spite of some uncertainty as to whether the doctrine of equivalents is allowed under the EPC, the E.U. has applied this doctrine 
The U.S Supreme Court has in the recent past held that one key aspect of the test for equivalency is interchangeability, “whether persons reasonably skilled in the art would have known of the interchangeability of an ingredient not contained in the patent with one that was."The Federal Courts (which are inferior to the Supreme Court) have also concurred stating that, “known interchangeability is often synonymous with equivalence."
Hesitancy of the U.S. to declare interchangeability as the sole test for equivalence may be due to the hardship of the test. In nearly all cases, experts will testify for opposing sides of the issue. And some critique Federal Courts for delivering rulings based upon subjective judgment, even though it purports to apply an objective rule.
Jurisprudence in the U.K. has been more clear than in the U.S., but still controversial. New rules for claim interpretation under the EPC were announced in Catnic Components Ltd. v. Hill & Smith Ltd. (the Catnic test).This test asks whether the variant has a material effect upon the way the invention works.
As for the U.S., the focus is on how the substitution of an element would affect the operation of the invention. The words used in the claim, rather than having a narrow technical meaning, may be interpreted figuratively and are deemed characteristics, or species of the term used. Therefore, interchangeability is determined by whether someone skilled in the art and informed of the invention and the variant, would indeed recognize the interchangeability of the elements at hand.
The U.S provides the broadest protection under the doctrine, counting foreseeable equivalents as infringing so long as they are not equivalent to an amended aspect of a claim, and unforeseeable equivalents as always infringing— with the caveat that unforeseeable equivalents have difficulty passing the way aspect of the equivalents test.
The United Kingdom does not consider itself to have a doctrine of equivalents; rather, it conducts a similar analysis under purposive claim construction. This analysis may or may not find an unforeseeable, after-arising technology encompassed in the claim, depending on the generality of the language of the claim. An unforeseeable (or foreseeable) equivalent that cannot be found within the meaning of the language of a claim cannot infringe. This requirement may place too much of an expectation on the drafters of a claim without giving significantly more guidance on patent scope.