The writer Arthur Conan Doyle knew about smoking guns. He used the expression in 1893 in one of his stories about the famous detective Sherlock Holmes.

In the story, a group of sailors rebel against the captain of a ship. Sherlock Holmes and others find the captain lying over a map, dead. Standing across from him is a clergyman with a gun in his hand. And not just any gun: a smoking gun.

The clergyman has just shot the captain! The smoking gun proves he is not a man of God, but a murderer.

However, there does not have to be a murder for there to be a smoking gun. In recent years, the expression “smoking gun” has come to mean any strong piece of evidence.

In the early 1970s, for example, many Americans suspected President Richard Nixon was covering up illegal activities by his aides. However, the president denied involvement in any crime. And there was no firm evidence tying him to criminal activity.

In the end, the Nixon White House gave Congress tape recordings that proved he had tried to hide information about the illegal activities. The release of the tapes forced him to resign from office.

Both politicians and the press called these Nixon’s smoking gun. They firmly tied him to a break-in at the Watergate building in Washington. Americans still call them Nixon’s smoking-gun tapes.

A politician or anyone involved in illegal activities can use a smoke screen to hide behind.

In the military, a “smoke screen” is a cloud of smoke created to hide military operations.

In conversation, a “smoke screen” is something that you do or say to take attention from something else or to hide your real purpose or intention.

If a smoke screen doesn’t work, you may want to use smoke and mirrors to hide your criminal behavior.

Years ago, magicians would use smoke and mirrors to fool their audiences. These days in conversation "smoke and mirrors" is anything people do to try and fool someone else.

However, if you are trying to hide a crime, your opponents or the police may try to smoke you out. To smoke someone out means to try to get them to come out of hiding. This comes from the practice of actually using smoke to make people leave an area.

"Smoke out" can also mean to bring someone or something into public view. The media is usually quick to smoke out a scandal. In the Watergate scandal, two Washington Post reporters, Bob Woodward and Carl Bernstein, were the primary people responsible for smoking out Nixon’s role in the cover up.

Even when Woodward and Bernstein did not have the tapes in their possession, they probably knew very early that something was wrong. As we say, “where there’s smoke, there is fire.” This expression means that if unpleasant things are said about someone or something, there is probably good reason for it. You may also hear it said this way: “There isn’t smoke without fire.”

After the public found out about the smoking-gun tapes, all the work Nixon tried to do during his presidency went up in smoke. If something goes up in smoke it is all wasted. When most people think of Nixon, they think of Watergate.

detective – n. a police officer whose job is to find information about crimes that have occurred and to catch criminals : a person whose job is to find information about something or someone