Gabrielle Giffords, a third-term member of Congress from Arizona, is in critical condition after being shot in the head Saturday. Authorities have identified the would-be assassin as 22-year-old Jared Lee Loughner of Tucson. Noted political assassins Lee Harvey Oswald, James Earl Ray, and John Wilkes Booth also used three names. So did the man who shot John Lennon, Mark David Chapman. And several notable serial killers— Gary Leon Ridgway, John Wayne Gacy, and Paul John Knowles —are also known by three names. (In fact, nine of the top 20 serial killers in the United States, ranked by body count , are known by three names.) Is there a reason so many murderers use their middle names?

It seems to be a coincidence. The three most famous political assassins in U.S. history used their middle names, but many others did not. For example, of the 12 people who have made legitimate attempts to kill a U.S. president, former president, or president-elect, only Booth, Oswald, and would-be Ford assassin Sara Jane Moore are commonly referred to by three names. Some references to Garfield assassin Charles Guiteau include his middle name, Julius, but others do not. If you don’t remember the other eight, two-named assassins on that list, it’s because most of them were unsuccessful. Consider Richard Lawrence, who failed spectacularly in his 1835 attempt to shoot Andrew Jackson, and John Hinckley Jr., who delivered a nonfatal wound to Ronald Reagan in 1981. There is one successful presidential assassin with only two names in the history books, but Leon Czolgosz has faded into relative obscurity along with his victim, William McKinley.

It’s often assumed that three names are used to identify an infamous killer so as to avoid cases of mistaken identity—so other guys named Lee Oswald wouldn’t have their reputations besmirched, for example. But some of the most famous three-named assassins identified themselves as such before they committed their crimes.

Oswald, for his part, appeared on the local Louisiana television program “Conversation Carte Blanche” in August 1963 to discuss his support for Cuban president Fidel Castro. Host Bill Slatter introduced him as “Lee Harvey Oswald,” and repeatedly used his middle name. Even though some of Oswald’s acquaintances referred to him as Lee Oswald, it’s not surprising that the press used the three-name version after he murdered Kennedy three months later.

John Wilkes Booth, a well-known actor, preferred to use his middle name in professional settings before he murdered Abraham Lincoln. Playbills listed him as either “John Wilkes Booth” or “J. Wilkes Booth.” Not all actors of the period used three names, though. Booth’s father and brother, Junius Brutus Booth Sr. and Jr., both used their middle names in playbills. But his more famous brother, Edwin, did not.

Garfield’s assassin, Charles Julius Guiteau, used his middle name in some settings but not others. So did the newspapers.

Some friends of James Earl Ray have publicly referred to him as “James Ray” since his conviction for the murder of Martin Luther King Jr. in 1968. But the assassin himself seems to have made a point of including his middle name in writing. He may have done so to distinguish himself from his father, James Gerald Ray. (Ray’s brother John Larry Ray was also named James Ray at birth, adding to the Ray family naming confusion, but John claims his birth certificate was the mistake of a drunken doctor.)

It’s true, however, that police often announce a suspect’s full name to avoid cases of mistaken identity, and reporters tend to follow their example. Mark David Chapman may be such a case. The press didn’t have any public statements from Chapman before his arrest, so they may have defaulted to the three names to avoid confusion with other Mark Chapmans. The decision was easier with Loughner, who referred to himself with three names on his YouTube page (although his MySpace page uses only two).

There may be an abundance of three-named killers for other reasons. Would-be assassins might embellish their own names to sound more grandiose. (Middle names were a point of pride when they first became popular in the United States in the 19th century.) Or it could all be a kind of feedback loop: Modern villains want to emulate their role-models.

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Explainer thanks Shailagh Murray of the Washington Post and Charles Savage of the New York Times.

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