One of the Prohibited Words is the phrase “prior art.” There is no reason whatsoever for the words “prior art” to appear in any patent application. Making any characterization of prior art is opening an avenue for attacking an issued patent and may unnecessarily complicate patent prosecution.
When someone cites “prior art” in a patent, they are making some characterization or drawing a comparison to what they think the prior art may be. In order to attack the patent, it may be possible to show that the prior art was actually something different or could be characterized in a completely different manner. This could lead to rendering the patent invalid through inequitable conduct, or at least show the patent in a bad light in front of a (non-technical) judge and jury who are hearing the case.
Characterizing prior art may complicate prosecution because one Examiner may take exception to your assertion that the prior art is one thing while another Examiner may characterize the same text as another thing.
Why open the door for an argument about the prior art? It benefits no one, particularly the client (who presumably has to pay for the agent/attorney to write a long-winded description of the prior art, in addition to paying for the extra prosecution and litigation problems down the road).
A well-drafted patent application should always talk about the invention in a positive, constructive light, and never compare the invention to what has been done before. It may be tempting to compare the invention to the prior art, especially when it seems easier than doing a proper description.
For example, our mousetrap invention may be described as “just like prior art mousetraps except with a photoeye sensor and mechanism for activating a snap mechanism.” Drawing a comparison to prior art serves no real benefit. A better description could be “a mousetrap that may use a photoeye sensor and a mechanism for activating a snap mechanism.”
Inventors and their agents/attorneys have a statutory requirement to disclose any prior art to the Patent Office. Not disclosing relevant prior art can render a patent invalid. The proper format for disclosing prior art to the Patent Office is through an Information Disclosure Statement. In an IDS, the Patent Office is made known that the prior art exists and is left to draw their own conclusions from the prior art. The Examiner may characterize the prior art in an Office action, and it would be proper to argue the characterization in a response, if necessary. But it serves no purpose to try to anticipate the Examiner’s characterization and argument, write a counterargument, and include it in the body of the patent application, which I have seen may practitioners do.
I don’t know if using any of the Prohibited Words rises to the level of legal malpractice, but overuse or sloppy use of terminology does indicate a low level of proficiency in patent drafting. My very first patent application, written without the help of a patent attorney or agent, was replete with the Prohibited Words.