Thanks, I needed that comma

How many commas are required in the following sentence?

According to a police spokesman because the threat was made over the phone the highest possible charge would have been harassment a misdemeanor.

The sentence in question was part of an exercise in my colleague's news writing class.

Ready for the answer? Three.

According to a police spokesman, because the threat was made over the phone, the highest possible charge would have been harassment, a misdemeanor.

My colleague was unsure about the final comma, the one after "harassment." I told him I was sure that a comma was needed, but I didn't know the rule. I have a pretty good "ear" for these things, but when people want to know the rules, I'm often thrown for a loop. I decided to look this one up in my trusty Associated Press Stylebook. Here's what I found. The final two words of the sentence are a "nonessential phrase," which is always preceded by a comma. Here's the Stylebook scoop from an entry titled "essential phrases, nonessential phrases":

An essential phrase is a word or group of words critical to the reader's understanding of what the author has in mind. A nonessential phrase provides more information about something. Although the information may be helpful to the reader's comprehension, the reader would not be misled if the information were not there.

Essential phrases are not set apart with commas.

Example of an essential phrase, also from the Stylebook:

We saw the award-winning movie "One Flew Over the Cuckoo's Nest." (The movie title is essential to the sentence because many films have won awards. It's not obvious to the reader that the author had this title in mind when writing the sentence.)

Example of a nonessential phrase:

We saw the 1975 winner in the Academy Award competition for best picture, "One Flew Over the Cuckoo's Nest." (Only one movie won the best picture award in 1975, so the title is not essential. Without the title of the movie, the reader might be confused, but the author's meaning is clear.)

In case you were wondering, the same rules apply for essential and nonessential clauses.