DEFINITION of Smoking Gun

A smoking gun is something that serves as indisputable evidence or proof, especially of a crime.

Here is an example used in everyday language from on Feb. 6, 2002: "Maybe there was no proof before, but there is now; a secret memo — personally handed to U.S. Vice-President Dick Cheney by Ken Lay ex-Enron chairman and CEO, which helps explain why the White House is so skittish about Enron and why Cheney and U.S. President George W. Bush stubbornly refuse to release the records of those energy task force meetings. The memo was obtained by the San Francisco Chronicle and reported exclusively there last week. This is the Enron smoking gun."


The phrase "smoking gun" calls up the image of a killer holding a gun that has just been fired as he stands over the dead body. The origins of the phrase seem to date to the short story "The Gloria Scott," which was written by Sir Arthur Conan Doyle and featured Sherlock Holmes. In the story, Doyle states, "The chaplain stood with the smoking pistol in his hand."


The phrase came into prominence in public conversation during the Watergate scandal of the 1970s. In June 1972, then-President Richard Nixon had a conversation in the White House with his aide H.R. Haldeman. In this conversation, he ordered Haldeman to get the FBI to cease investigating the Watergate break-in, coming up with various excuses to use for the order. The conversation was taped. When the existence and content of the audio tape came to light in 1974, it revealed that Nixon had himself been involved in the Watergate cover up and had obstructed justice. This tape was referred to widely as the "smoking gun" tape. In fact, the House Judiciary Committee investigating had already been asking "Where's the smoking gun?" in its efforts to link Nixon to the initial Watergate break-in and the subsequent cover up.


The phrase was widely revived in 2003 in the search for the weapons of mass destruction that some claimed were being manufactured in Saddam Hussein's Iraq. Teams searching for incontrovertible evidence that these weapons existed were said to be looking for the "smoking gun." U.N. officials and reporters all used the term with this very specific meaning.

The term "smoking gun" has also migrated over to the field of science in recent years. In 2014, a discovery of gravitational waves combined with a new theory regarding the rapid inflation of the universe at its beginnings were roundly cited as the "smoking gun" providing the validity of the Big Bang theory.