Legal malpractice is sometimes just about missing a deadline.  Sometimes its just about being lazy.  One recurrent theme is attorneys taking on a field in which they do not understand the subtle problems.  Here is an example:

"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 an Examiner may take exception to your assertion that the prior art is one thing while the Examiner may characterize the same text as another thing. 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. "