I. Lewis (Scooter) Libby Jr. will be in a courtroom for the next few weeks as his perjury and obstruction of justice trial in relation to Plamegate, unfolds. A number of witnesses will be journalists.

An excerpt from the NYT story:

They will be asked to recount conversations they had in 2003 with Mr. Libby, then Vice President Dick Cheney’s chief of staff, that were undertaken with some understanding that they were confidential.

The highly unusual spectacle of journalists giving testimony at a criminal trial about their reporting is a result of the intense investigation into the disclosure of the identity of a Central Intelligence Agency operative. Previous leak investigations typically ended in failure as reporters were able to fend off prosecutors’ efforts to delve into what they learned from government sources.

But in trying to determine how Valerie Wilson, who was known by her maiden name, Valerie Plame, came to be identified as a C.I.A. operative in a newspaper column in July 2003, the prosecutor, Patrick J. Fitzgerald, successfully pressed reporters to testify before a grand jury, threatening jail if they refused. In the case of one, Judith Miller, formerly of The New York Times, Mr. Fitzgerald, with the backing of the courts, succeeded in having her jailed for 85 days until she relented.

Rodney A. Smolla, the dean of the University of Richmond Law School and an authority on the First Amendment, said the Libby investigation had made clear that any promise of confidentiality from a reporter now comes with an asterisk.

“This has undercut the assumptions that existed for several decades that a reporter’s promise of confidentiality is not only sacrosanct as a matter of journalistic ethics but relatively secure as a matter of law,” Dr. Smolla said. “Now it’s clear that the legal system will try to break that promise, and the sources and reporter appear much more vulnerable, at least in the federal system, than was thought to be just a short time ago.”

There is no formal code that describes the rules of engagement for officials and reporters in Washington, but a less-than-neat system evolved over decades that allowed government sources to impart information to journalists without having their identities revealed publicly. Editors, hoping to be more accountable to the public, have tried in recent years to change those practices.

Nothing may have shaken those ways of doing business and the underlying relationships as much as the Libby case.

The impact in the workaday world is difficult to measure, as it is impossible to know of articles never written because officials decided not to risk becoming sources. Eve Burton, vice president of the Hearst Corporation, said her company had refrained from publishing or broadcasting stories in recent months to avoid the risk of becoming embroiled in a subpoena battle that could lead to fines and jail terms for reporters.