FROM the headlines, the story looks quite straightforward: "Journalist Sentenced in Child Porn Case"; "Reporter Pleads to Porn". They describe a case in which a prominent US journalist received an 18-month jail sentence this week after pleading guilty to one count of receiving online child pornography and one count of distributing it.

But the case is far more complicated. The journalist, Larry Matthews, is an award-winning, veteran investigative reporter who is currently a producer at well-respected US public service broadcaster, National Public Radio.

He has also done work on child pornography in the past. In 1995, he produced a three-part series for a major Washington, DC, radio station on the boom in Internet child pornography.

Advocates of the American Constitution's First Amendment, which protects the freedom of the press along with other civil rights, are worried that the case threatens to set a precedent which could stifle investigative reporting.

According to the journalist and his attorneys, Mr Matthews was involved in obtaining and trafficking in child pornography files when apprehended in 1997 because he was working on a story about child pornographers which he hoped to sell to a magazine.

He was therefore frequenting the secretive, sleazy online chatrooms in which such material was made available. But FBI agents were using the same approach to seek out porn merchants. Mr Matthews seems to have tried to deal in porn files with investigators, who then charged him with 15 counts of distributing and receiving online child pornography. Each count carries a possible 15-year prison sentence. Mr Matthews argues that the nature of the story - which was to include an examination of how US law enforcement has gone about pursuing child pornographers - required him to understand how such material was distributed.

But he was never allowed to present this defence during his trial. Last year, a federal court judge decided that the fact that Mr Matthews was a member of the press did not allow him to break the law. In other words, investigating a story is not an extenuating circumstance in this case.

According to the federal judge's preliminary ruling barring a First Amendment defence, "The law is clear that a press pass is not a licence to break the law". Thus, he was explicitly barred from explaining that he was researching a story.

So he and his lawyers decided on a riskier approach. Rather than go through a court trial in which he was prohibited from mentioning his investigative work, they decided he would offer a conditional guilty plea, receive a sentence, and then appeal it through the US court of appeals. If the court overturns the lower court's ruling, he can return to court and change his guilty plea, then defend himself pleading protection under the First Amendment.

A range of media organisations and First Amendment legal defence groups filed briefs in the original case in support of Mr Matthews's right to at least make a First Amendment defence: the American Civil Liberties Union (ACLU) of Maryland (the state in which the case was heard), National Public Radio, the American Federation of Television and Radio Artists, and the Radio-Television News Directors Association.

The prosecution, backed by the FBI, argued that Mr Matthews possessed the files for personal use. They claimed that, if Mr Matthews was able to claim protection as a reporter, child pornographers would have a quick defence for their activities. They insisted the First Amendment defence was rightly excluded - otherwise, one lawyer said, a reporter investigating the drug trade would be excused for buying and selling drugs.

But Mr Matthews's lawyer says he believes the precedent, if the ruling is allowed to stand, will open the door for almost anyone doing investigation on the subject of online child pornography to be prosecuted, including lawyers, psychologists, academics and legislators preparing anti-porn bills.

Furthermore, the ACLU fears the ruling could not only curb investigative work in general on the Internet but also cordon off law enforcement from outside investigation. "In particular, news-gathering concerning the Internet activities of both wrongdoers and law enforcement officers could be severely handicapped if Matthews is not permitted to raise a First Amendment defence here," according to the ACLU's brief.

"Thus, the court must carefully weigh the potential chilling effect of permitting federal agents to arrest and convict reporters who attempt to monitor the role of law enforcement on the Internet."

Could the same scenario happen here? Perhaps. US law enforcement tends to react with Pavlovian predictability to any perceived transgression involving child pornography. Yet the courts have tended, like their European counterparts, to uphold the rights of journalists to obtain material for investigative work. Still, most US legal experts had predicted that the Maryland court would allow the First Amendment defence it eventually rejected.

Child pornography is one of the most tainted and emotive subjects in the online world, which makes this case particularly difficult. We're forced first to measure our belief that Mr Matthews was only in possession of such material because of an investigation. And then, we must decide whether the investigation itself outweighs other legal imperatives.

The eventual outcome will determine further the legal shape we try to slap on the uses - and abuses - of the Internet.

Karlin Lillington is at Klillington@irish- times.ie