The leak is about as old as the secret. People who control secrets hate leaks, except when they create them. That is why it is said that the ship of state is the only kind of ship that leaks from the top.
Unplanned leaks tend to enrage those who control secrets because they undermine their sense of control. President Reagan once complained that he was "up to my keister" in leaks. President Nixon was tempted into sponsoring a self-destructive break-in on a psychiatrist's office out of rage against Daniel Ellsberg's leak of the Pentagon Papers.
Leaks from law-enforcement agencies can be quite harmful. A leak of plans of ATF federal agents to enter the Branch Davidian compound in Waco in 1993 alerted David Koresh and resulted in the death of four of the agents. The leak that Richard Jewell was a suspect - innocent, as it turned out - in the Atlanta Olympics bombing damaged his reputation and led to libel suits. The leak to CBS of FBI plans to raid the Unabomber's shack in Montana could have alerted him to escape if CBS had not acceded to an urgent FBI request to delay breaking the story.
A special subsection of leaks is the so-called grand jury leak - so-called because it usually does not come from the grand jury itself. This concerns investigative material in unevaluated form that may or may not lead to an indictment. A leak of grand jury information may hinder an investigation, and it may damage an innocent person. It is a crime to leak grand jury information. It is not a crime for a reporter to receive such information, but, theoretically, the reporter could be called as a witness to a crime.
Vice President Spiro Agnew's lawyers actually got a judge to issue subpoenas for journalists who had reported his sealed indictment on tax-evasion charges, but his plea bargain made that issue moot. In 1973, Watergate judge John Sirica threatened reporters Bob Woodward and Carl Bernstein with sanctions if they did not stop trying to contact grand jury members.
The worst mistake Woodward and Bernstein made was to report prematurely that former Nixon campaign treasurer Hugh Sloan had testified about a Watergate slush fund to the grand jury. The most authentic grand jury leak on Watergate enabled CBS to reveal that the grand jury, told it couldn't indict President Nixon, had named him as an unindicted co-conspirator.
If once the grand jury leak was an occasional happening, today it is an almost-daily occurrence, a weapon in the deadly competition between President Clinton's persecutors and his defense. It may or may not be a coincidence that most recent leaks - right, wrong, and somewhere in between - tend to put pressure on the president and on former intern Monica Lewinsky.
Leaks today are less like a drip than a gusher, propelled by some prosecutorial El Nio.
* Daniel Schorr is senior news analyst for National Public Radio.