I’m reading a lot of opinions as a 1L. I notice that some judges use and some judges omit definite articles with the terms “plaintiff” and “defendant.” Is one style preferable to the other?
The plaintiff averred that he was shat upon by said monkey.
or
Plaintiff averred that he was shat upon by said monkey.
I think it depends on context but doesn’t really matter, generally. If you are a clerk writing an opinion for a judge, you’ll do what the judge prefers. If you’re writing your own opinion as a judge, you can do whatever you want. In complaints or other pleadings, often “Plaintiff” and “Defendant” are used as direct substitutes for the names of the parties, and in that case it is common to omit the definite article. In a moot court brief, you would probably want to use whatever sounds natural, and so standard English rules would apply. I don’t know of any specific preferences for one or the other, but it’s possible that law school professors, judges, colleagues, supervising attorneys, or senior partners that you come into contact with may have their own preferences in certain contexts. I think most people won’t care either way as long as what you write doesn’t sound extremely awkward.
You got a cite for this? 
I’m no lawyer but I’m a contracts professional - with contractually (or legally) defined terms articles are considered superfluous. Let’s say, in a purchase and sale agreement, John Doe is formally defined as the “Purchaser” and Joe Smith is defined as the “Vendor”. Thereafter, in the document, proper drafting would say “Purchaser shall pay to Vendor” rather than “the Purchaser shall pay to the Vendor”. I would imagine this convention with formally defined terms would be reflected in all areas of legal work. It’s not wrong to use the articles, and in verbal communication/negotiations dropping the articles might sound awkward, but when preparing legal documents articles aren’t usually used with defined terms.
I also omit the definite article when refering to the specific Plaintiff or Defendant in my case. I also capitalize. Like someone said, it’s like using a defined term (even though I omit the definition as superfluous/obvious.)
If I’m discussing the facts in a precedent, I’ll use the article, with
no caps: “In Moorman, the plaintiff claimed damages gradually resulting from a leaky storage tank. Here, Plaintiff’s losses arise from a sudden, catastrophic event.”
I find the distinction useful, although I don’t claim that this practice is anything other than style.
I follow Random’s use. When writing about a plaintiff in another case, I use the article so as not to confuse the reader with the plaintiff in the instant case.
If I have not defined the term in a document, I use a lower-case "p"laintiff or "d"efendant. Once the term is defined, I use caps. For example:
On January 2, 2003, plaintiff John Smith (“Plaintiff”) sent defendant Bob Jones (“Defendant”) a letter demanding payment pursuant to the terms of the Widget Purchase Agreement (“Agreement”) executed on June 6, 2002. Plaintiff received no response to the demand letter and filed a complaint against Defendant on February 3, 2003, alleging, among other things, breach of the Agreement. In that complaint, Plaintiff also named defendant Dave Brown (“Guarantor”) because Guarantor guaranteed Defendant’s debt to Plaintiff. Defendant and Guarantor are collectively referred to herein as “Debtors”.
You get the idea…
However, I always define my terms just because it’s a good habit to get into. YMMV.
Any law student is well-advised to supplement Black’s Law Dictionary with Bryan Garner’s A Dictionary of Modern Legal Usage. It answers questions like this one, as well as providing usage advice for legal terms and whole categories of potential solecisms.
In this case, Garner also recommends that capitalization and omission of articles be used in the instant case, except where an article will prevent confusion.
Garner is the editor of Black’s Law Dictionary, the author of A Dictionary of Modern American Usage, and a founding member of the H.W. Fowler Society.
I’m not an attorney, but I have been a legal word processor for a few years. The use of an article with a defined term seems to be a matter of preference, however, a non-defined term should always use an article. Omitting the article emphasizes the fact that the reference is to the instant case rather than to a cited case or simply a generalization. In some contexts this distinction may avoid ambiguity.
I have seen a junior associate draft a document using articles, a senior associate take them out, and a partner put them back in (sigh - the joys of word processing). The most important thing is to be consistent throughout the document.