Patent Drafting Tip: Take Care with Open-Ended Descriptions

Be careful with the conventional wisdom that tells a patent drafter to use permissive, open-ended language when describing features of an invention.  Like me, you may have been taught to avoid “patent obscenities” like “invention,” “objects,” etc., and to use permissive helping verbs wherever possible, i.e., “the widget [could, might, can, may, etc.] be blue,” rather than “the widget is blue.”  Be careful: the conventional advice is good advice most of the time – but not, I believe, all of the time.

Consider this patent drafting guideline:

A patent specification should use verbs of possibility by default. However, in describing various embodiments, use limiting verbs for features that are necessarily present in every embodiment.

This is guidance for lawyers, so of course it comes with many caveats. Often there is a gray area encompassing the line between features that do and do not truly limit the invention.  Thus, as the rule suggests, err on the side of open-ended language. But be mindful of instances where permissive language can hurt, and will not help.

First, a reminder why the selection of an open-ended versus a limiting verb matters. It’s pretty simple. Open-ended or permissive verbs provide support for claim language without, the theory goes, potentially limiting the scope of the claim. In the above example, describing the widget in the specification as possibly blue allows a claimed widget, so long as the claim does not specify a color limitation, to be blue or possibly some other color. On the other hand, if the specification says simply “the widget is blue,” then an accused infringer making, using, or selling red widgets will have an argument for a claim construction limiting claimed widgets to the color blue.  Sure, the patentee might still be able to enforce against red widgets.  However, at a minimum you risk a costly argument, and at worst you allow infringers to escape enforcement, probably based on a feature that is not even critical to the inventive concept.

Now, if definite, limiting language can be used to restrict claim scope and allow potential infringers to get off the hook, why would you ever use it? Some might say that this is a rhetorical question, because everything in a patent specification should be couched in terms of example and possibility. I agree that it is a good idea to err in in the direction of permissive language. But think about whether open-ended language can increase a claim’s exposure to prior art, and maybe even give rise to indefiniteness under 35 U.S.C. § 112(b), without expanding the scope of the claim against potential infringers one iota.

To put this another way, what if the widget being blue is part of the widget’s essential being, part of the widget qua widget?  Consider a slightly more complex hypothetical. Suppose you have a patent claim directed to an apparatus that comprises a “stringed musical instrument.” Suppose further that the claimed invention is only applicable to stringed instruments played with a bow, i.e., there is no possible way that a plucked instrument such as a guitar or a harp could be used to infringe a claim. In this instance, your patent specification should state that the instrument being discussed “is” played with a bow, not that it “could be” played with a bow.

Why?  Remember, we have determined that there is no possibility that someone could infringe with any other kind of stringed instrument, i.e., a non-bowed instrument.  Any embodiment of the inventive concept to be claimed only makes sense with instruments played with a bow.  On the other hand, a patent examiner or accused infringer might want to use prior art pertaining to plucked stringed instruments against certain features in the claims.  Clear, limiting language in the specification, which could even be added to the claim if warranted to expedite patent prosecution, can help limit the scope of prior art that a patent examiner or accused infringer can apply. And it will be harder for anyone to argue that it is unclear what kind of stringed instrument is covered, and that therefore your claim is indefinite, or that your specification lacks adequate written description.

This post is part of an occasional series discussing patent preparation and prosecution tips and tricks.

Like all posts on this blog, this post is not legal advice and does not establish an attorney-client relationship. As any competent practitioner understands, preparing and prosecuting a patent application is often informed by subjective factors, will vary from application to application, and may be done differently by different reasonable and competent practitioners. The above is an abstract discussion to provide food for thought, and not commentary about what should or should not be done on any particular set of facts or in any particular real-world situation.


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