In a dramatic turnabout worthy of Hollywood, Time magazine reporter Matthew Cooper has decided to testify about his source to a federal prosecutor investigating the government leak of the identity of covert CIA operative Valerie Plame. Had he not done so, Cooper would be in jail by now — which is exactly where New York Times reporter Judy Miller is as of this hour. At the same sentencing hearing, Miller (who never wrote a word about the subject, but who did gather material) refused to reveal her source to Federal Judge Thomas Hogan, and was held in contempt. Cooper said he’d been prepared to do the same, but had heard at the last minute from his source, who told Cooper, “in somewhat dramatic fashion,” to feel free to release the source’s identity in grand jury testimony.

According to the Washington Post, special prosecutor Patrick J. Fitzgerald already knew the identity of both Miller and Cooper’s sources; he discovered the identity of Cooper’s source when Time turned over Cooper’s notes and emails. Fitzgerald himself said it would be “pointless” for Cooper to go to jail, and the source apparently agreed, based on the conversation Cooper cited in court today. It’s difficult not to be sympathetic to Cooper’s desire to avoid what would have been imprisonment to protect a source who was seemingly already out in the open.

But while we sympathize, we can’t defend his decision. Cooper’s imprisonment might not have helped his source, but it would have sent a message on behalf of journalists everywhere — as Judith Miller has done — that they will not buckle under government pressure. The facts aren’t all in yet, but it appears that Cooper’s source gave him permission to testify only when it became clear that Cooper was almost certain to go directly from the courtroom to jail; otherwise, that permission would have come long ago. In effect, the government used Cooper’s impending incarceration as a lever to bludgeon his source — and both the source and Cooper gave way.

In a press conference today, Cooper explained that he had not been swayed by the general waiver of confidentiality signed earlier by his source, since it had been obtained under duress. But is not the same true of the personal waiver Cooper received at the last minute? Since Time Inc. had already pulled the rug out from under its reporter, over his objection, by handing over documents naming that source, the source had nothing to gain from Cooper staying silent and going to jail. But he or she did have something to lose: It would have looked selfish and callous for the source to stand mute and let Cooper go to jail when his or her identity had already been revealed. So the source, backed into a corner by the federal prosecutor, did what made sense — he or she freed Cooper from his obligation. It was a decision made under duress, just as surely as the decision to sign the general waiver of confidentiality was made under duress.

In that sense, Cooper’s reliance on the source’s personal communication for his decision rings somewhat hollow. He still had the option of taking a stand for journalistic principle; he still could have refused to buckle under to a prosecutor seemingly dead set on establishing once and for all that journalists don’t have the right to protect their sources from the government.

Anonymous sources are too often used irresponsibly. But they are essential to a healthy press corps, a healthy body politic and an informed public. (See Woodward, Bob.) Cooper’s decision seems certain to make sources who know things that the public should know less likely to reveal them, and reporters who should pass that information on to their readers less confident that they will be supported by their bosses if hauled before a judge.

Brian Montopoli is a writer at CJR Daily.