The spring edition of The Journal of Appellate Practice and Process has an interesting article in it: "Does the readability of your brief affect your chance of winning an appeal?" by Lance N. Long and William F. Christensen. These are professors who do statistical analysis about legal writing, e.g.,their previous article "Clearly, Using Intensifiers is Very Bad – Or is it?," appearing at 45 Idaho L. Rev. 171 (2008).
The bottom line conclusion from their foray into readability is no, it doesn't impact results. Readability was measured by the length of words and sentences. So basically, there is no statistically significant indication that verbosity affects results.
I don't think that's a giant surprise — if anyone can handle those long SAT words, it may be judges, and it's a comfort to think that they can dig through verbosity to rule on the merits. I would not call this a ringing endorsement to draft endless Ciceronian sentences full of those SAT words, however. Interestingly, the study "does show … that the opinions of judges and justices are less readable than lawyers' briefs and that the opinions of dissenting judges or justices are the least readable of all the appellate writing we analyzed." Hmmm.
In terms of relative readability, so defined, US Supreme Court writings, from the Court and lawyers, are all less readable on average than the writing of their counterparts in the state supreme courts and federal courts of appeals, with the writing of the lawyers before the U.S. Supreme Court, in turn, more readable than the Court writings.
In sum, according to these professors, the U.S. Supreme Court materials are the least readable, i.e. using the longest words and sentences, with the Court itself the most verbose and dissents are less readable than majority opinions across the board. The most readable writing appears to be in appellee briefs in the federal courts of appeal.
As to the results of reported in these professors' earlier article on the use of intensifiers, that statistical review is also illuminating. Basically, their results, they say, show that the frequent use of intensifiers, particularly by an appellant, is associated with a statistically significant increase in adverse outcomes for the intensifier user. That confirms the general view, I think, that there is no place for adverbs and adjectives in your brief – get rid of them. Every clerk after the first week of work knows that when a lawyer says "clearly," it means s/he has no actual legal support for what they are saying. The article also indicates that there's some support for the conclusion that lawyers who use a lot of intensifiers make more grammatical errors, and that could also be impacting results.
Notably, there is one exception to this general rule against using intensifiers. Dissents by judges use significantly more intensifiers than the majority – again no surprise, I suppose, because they are exorcised by the majority ruling. But, interestingly, if an appellate opinion does use a high rate of intensifiers, an appellant's brief written for that appeal that also uses a high rate of intensifiers is associatied with a statistically significant increase in favorable outcomes.
What does this exception mean? Nothing too useful for the practitioner, I think. The professors write "the odds of reversal can actually be higher for appellants who have high intensifier usage rates, but only when the judge writing the opinion is also a prodigious user of intensifiers." If you are appearing before a single judge and his or her opinions have lots of intensifiers, perhaps this means you can fire away. But you are usually dealing with a panel. As these professors say, "[f]or the majority of cases, however, the conventional wisdom that intensifiers are associated with losing arguments is validated."
My takeaway from these articles is that intensifiers remain a no-no, and while it's heartening that I can use a three-syllable word or a lengthy sentence when appropriate, I'm still going to try to be clear and concise, and use plain language. I'll leave all those Henry James sentences and highfaluting SAT words to Supreme Court dissenters.