Of all punctuation marks, the comma is the one most often debated in courthouses; its presence or absence in statutes and other legal texts has determined the outcome of cases—going back in U.S. history to at least 1872, when the inexplicable insertion of a comma between the words fruit and plants in the new version of the nation’s import law defining items exempt from tariff resulted in a $2 million loss to taxpayers. (Crockett, The Most Expensive Typo in Legislative History, priceonomics.com (Oct. 9, 2014).)

Across the Atlantic, the question of a comma famously became a matter of life and death in one case. In Rex v. Casement (1916) 1 K.B. 98, an Irish nationalist was found guilty of treason because of an appellate court’s willingness to read a comma into a particular place in an English translation of a statute defining treason dating from the Middle Ages. According to a 1917 transcription of the hearing, two judges noted that the Norman text of the law in the “Statute Roll” and the “Parliamentary Roll” differed in some respects. At one point, discussion turned to whether a mark on the original roll represented a comma, a bracket, or a 565-year-old fold in the paper. Ultimately, the appeal failed and Sir Roger Casement was hanged. (Read legal blog writer Mark Anderson’s pithy account HERE.)

Just this year, an appellate court’s refusal to read a comma into a statute determined the outcome of a case, though this time it was only a matter of money.

The United States Court of Appeals for the First Circuit’s conclusion that the lack of a comma in a particular part of a state overtime law probably was intentional resulted in truck drivers winning an estimated $10 million against a Portland, Maine dairy company. The entire opinion turned on a particular usage of the comma, that being, in a series of items joined by a conjunction. (O’Connor v. Oakhurst Dairy (1st Cir. 2017) 851 F.3d 69.)

Writers can avoid the common source of grammatical confusion represented by the dairy company case by following this simple rule: “When a sentence contains three or more items joined with one conjunction, put a comma after each word except the last.”

That’s how Richard Wydick states the tip concerning the serial or “Oxford” comma in Plain English for Lawyers (5th ed.).

Whether to adopt the serial comma is “not even a close call,” says Bryan Garner, Wydick’s fellow advocate of plain English in legal writing.

“Omitting it may cause ambiguities, while including it never will,” he says in The Elements of Legal Style (2d ed).
Here’s the example Garner offers in The Elements to illustrate the confusion that failure to use a serial comma can cause:

The investor asked for separate reports on the performance of her investments in real estate, commodities, coins and stocks and bonds.

How many reports does the investor want? Placement of a serial comma would clear that up:

real estate, commodities, coins, stocks, and bonds (five reports)

real estate, commodities, coins and stocks, and bonds (four reports)

While journalists following the Associated Press Stylebook typically leave out the serial comma—ostensibly to save space in the narrow columns of a newspaper—it is widely used in academic writing and books. For example, use of the serial comma is the style of the Oxford University Press (hence, the term, “Oxford comma”). Some experts have declared the debate essentially over. The serial comma is now “almost universally preferred, at least in the United States,” says, for example, Christopher Lasch in Plain Style (Stewart Weaver ed.).

Attorney Savannah Blackwell is a former news reporter who covered government and politics for more than a decade, mostly in San Francisco. She can be reached at savannah.blackwell@gmail.com. Follow her on Twitter at @SavannahBinSF.