One question I often receive is whether or not to use a comma with who. Let’s look at two examples, one with a comma and one without, and learn when to use the comma with who. Both examples come from the Associated Press, which generally has correct punctuation in its news stories.
Example 1: No Comma with Who
John Fenton Wheeler, an Associated Press foreign correspondent who was the last U.S. reporter expelled from Cold War-era Cuba, has died. (http://www.ap.org/Content/AP-In-The-News/2013/Former-AP-correspondent-Wheeler-dies-at-88)
In this example, the clause beginning with who tells the reader which correspondent. Here, “an Associated Press foreign correspondent” could refer to many people, a group of people. To tell the reader which person in this group the article is about, the who clause is necessary information.
The “official” name for the clause is restrictive clause. The clause restricts our attention from the group of people to just one person. It provides necessary information and cannot be separated from the word, correspondent, that it describes. As such, the writer correctly did not put a comma before who.
This sentence follows Zen Comma Rule V: Dont use commas to separate restrictive phrases and clauses begining with who.
Example 2: Comma with Who
Dave O’Hara, who covered Boston sports greats from Ted Williams to Larry Bird during a 50-year career with The Associated Press, died Wednesday. (http://www.ap.org/Content/AP-In-The-News/2013/Former-AP-Boston-sports-editor-OHara-dies)
In this example, the entire clause beginning with who is separated from the rest of the sentence with commas. We see the comma before who and the comma after Press. Here, the entire clause provides additional description of Dave O’Hara. The information, while interesting, is not necessary to tell the reader which person is being described.
The “official” name for the clause is non-restrictive clause. The descriptive clause beginning with who does not restrict the readers’ attention from a group of people to just one person. In fact, it can’t: Dave O’Hara is already just one person. For this reason, the information is not necessary for the reader to know whom the article is describing. The clause can be removed, and the readers will still understand the message of the sentence, including the person about whom the writer is writing. As such, the writer correctly used a comma before who and another after Press, thus separating the clause from the rest of the sentence.
This sentence follows Zen Comma Rule U: Use commas to separate non-restrictive phrases and clauses starting with who.