On December 1, 2004, David Casiano was on trial, facing criminal charges relating to drug possession, when he noticed that an undercover police officer was present to testify against him. With camera-equipped cell phone in hand, Casiano exited the court room and acted as if he was taking photographs of the undercover officer and other police officers who were in the hallway outside.

Those officers complained to the judge, who ordered that the phone be confiscated. Casiano was reported saying, after his phone was seized: "What do you think I am...stupid? I already e-mailed the pictures to my house before you took the phone."

A court officer who was asked to inspect the cell phone could not find any photographs of either the undercover officer or any of the other police officers, and couldn't even determine whether the phone was capable of sending e-mail messages.

That led Casiano, 37, to be additionally charged with witness intimidation. (A local news report says he pleaded guilty to and went to jail for trespassing charges related to his original drug charges. Court records say the jury returned a not-guilty verdict on the original drug charge.)

During his subsequent trial on the witness intimidation charge, Casiano essentially invoked the I-was-just-kidding defense. He produced an affidavit from T-Mobile saying his cell phone wasn't even operational on the day of the incident. But the judge rejected it, saying the affidavit was not relevant, apparently on grounds that the threat of a photograph was what mattered. Casiano was found guilty, and he also lost on appeal.

This raises the obvious question: Under what circumstances should defendants--or members of the news media, for that matter--be able to publish photographs of undercover police officers or police informants? And when can merely taking a photograph constitute "intimidation?"

Police have already been alarmed at Web sites like Who's A Rat, which collect reports of alleged police informants and make them available publicly. Boston-area disc jockey Sean Bucci launched Who's A Rat when he was facing his own marijuana charges, and The Boston Globe reported that it outed at least one paid informant for the FBI in Boston.

But because the First Amendment's guarantee of freedom of expression likely protects such Web sites, Who's A Rat remains online.