On its face, the policy argument for the Patent Office's use of the Broadest Reasonable Interpretation (BRI) when examining patent claims makes sense. Namely, during examination we want the Office to make sure that under the broadest possible interpretation, the claims are still patentable. That way, during later enforcement, only valid claims can be asserted and their scope cannot be stretched beyond what the Examiner considered.

Unfortunately, there are fundamental problems with this line of reasoning. Some of the problems result from practical implications while others come from logical gaps in the policy arguments. 

First, no matter how thorough the examination, there is always "new" prior art found during enforcement. This is because the nature of our legal system - defendants want a new argument for invalidity, not one that the examiner has theoretically already considered. So, no matter what we do with claim interpretation during examination, there is and will always be new prior art identified by defendants in patent litigation. This truth is universal around the world and further validated when one considers all of the non-patent literature sources of prior art available via the Internet - something most patent examiners do not have the resources to effectively search and consider. Defendants in litigation will always be more incentivized and likely better equipped to find prior art than a patent examiner.

Second, in practice, the BRI creates a perversion of the examination process.  An examiner tasked with rejecting applications (e.g., incentivized to reject applications, as is the current state of affairs) will use the tools available, including the BRI. No one can fault the Examiner for taking this approach - it is the system the Examiner is encouraged to use. Further, as stretching claim scope eases the ability to reject, it is not surprising that often the driving force behind a BRI issue is that the alleged interpretation just happens to make the prior art rejection stronger. However, easing the ability to reject applications should not be a justification for the BRI. For example, just as biasing the examination process against applicants would reduce the chances of invalid patents from being issued, no one can seriously suggest that a good solution is to simply to create unfair processes (i.e., eliminate the right to due process).

As an example, consider the simple claim term of a "four bar linkage." Engineers know what this is;  but, if the term is broken down term by term, with each term using its ordinary English meaning, an Examiner can argue under the BRI that numerous meanings are possible, such as the following:

• a device for linking elements (linkage) comprising 4 pipes, or
• four bodies and four joints with a single degree of freedom.

Each of these could be argued to be reasonable, but they are of significantly different scope. As a result of bad experiences with the BRI, most patent drafters' now have the natural tendency to include much more detailed examples in the specification with ranges of claim scope meaning so as to enable successively narrower options. That way, if a BRI issue comes up, the least amount of amendments can be made as is possible. However given that one never knows which element of a specification will have the BRI problem, this means that every element in the specification should be painstaking described with varying levels of scope. Such additional work drives up patent specification length considerably, often doubling or tripling the overall word count of a specification. In turn, costs increase both to the applicant and the Office, whose examiners must now read and search through significantly longer applications. All because of a system that relies on a claim interpretation that is often not what any applicant ever intended.

Third, the idea of the "broadest" interpretation is in tension with the idea of a reasonable interpretation. There is little reason to think that the broadest interpretation is a reasonable interpretation. By its very nature, the notion of the broadest interpretation means finding the limits of the interpretation, not the bull's eye of reasonableness.