The legal writer must know the law, to distinguish everything and only that which advances the client's cause. Prolix irrelevance is the most glaring offense in legal writing, but relevance, unlike concision's other aspects, emerges from legal understanding rather than writing skill. Prolixity always injures the court's comprehension because writing conveys meaning through patterns of inclusion and omission, prolix irrelevance miscuing the court.
Avoiding prolixity operates in tension with another commandment, avoiding superficiality. While strict relevance is more important than trial attorneys realize, thoroughness trumps relevance when they conflict, as happens when the writer doesn't fully grasp the relevant law's contours. Omitting a crucial contention often waives it. Every competent attorney has a healthy fear of waiver and, if in doubt about relevance, errs toward inclusion.
The treatment for prolixity consists of understanding applicable law. Your ghostwriter should learn the governing substantive law before writing your brief. The ghostwriter should have an exceptional understanding of procedural law, the law of evidence, and the law of remedies, since these laws constrain relevance.