It sounds like something James Bond would carry: A knife that's also a gun.
But it is the kind of thing police officers are warned about from time to time, just as they are about guns disguised as belt buckles and tire gauges and motorcycle handlebars modified to fire a shotgun round.
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The knife-gun, which isn't well known outside of gun enthusiast circles, has pushed its way into the case surrounding the 2014 killing of Laquan McDonald, a black 17-year-old who was shot 16 times by a white Chicago police officer, Jason Van Dyke.
The city released more than 300 pages of police reports and other investigation documents late Friday pertaining to the case, including a December 2012 bulletin warning officers about a "revolver knife" and a reference to Van Dyke remembering the bulletin.
During an interview with his superiors about the sequence of events and his decision to use deadly force, Van Dyke said he was aware of throwing knives, spring-loaded knives that propel a blade and he "recalled a previously issued Chicago Police Department bulletin warning of a weapon which appeared to be a knife but which actually was capable of firing a bullet, making it a firearm."
Internal investigators searched the department's message center and found a bulletin issued in 2012 warning officers of a "revolver knife" capable of firing .22 caliber cartridges.
Though a cursory Internet search by The Associated Press didn't turn up any references to officers in Chicago or other U.S. locales being shot with such a weapon, the bulletin could find its way into the argument Van Dyke's attorney has been making — that McDonald feared for his own safety when he shot McDonald.
"I remember back in the late 80s and early 90s about a shotgun affixed to the driver's door," said Dean Angelo, president of Chicago police officers' union. "Police officers are warned about these things."
Police departments have been aware of the existence of knife-guns for several years. In 2002, for example, law enforcement officials in London voiced concern over a knife equipped with a firing mechanism hidden in the handle that allowed it to fire five bullets.
Three years later, the Commission on Peace Officer Standards and Training in California issued its own training bulletin that included photographs of a "knife that conceals a revolver in its handle."
Such weapons have been around for centuries, really.
An article on Guns.com describes a hunting knife and wheel lock pistol that was made in Germany in 1546. In the 1830s, the U.S. Navy came up with the Elgin pistol, which was a pistol with a knife attached to it.
According to the article, an Illinois company in the 1950s started selling a folding pocket knife that was also a gun. Then in the late 1990s, a company called Global Research and Development "designed the world's first production fixed blade knife that held a multi-shot firearm inside its grip," the website reported.
No listing for the company could be found and Guns.com reported that it seemed to have folded eight or nine years ago. Possibly that's because the knives did not prove very popular, with the article saying less than a thousand were made.