Such cases are a relative rarity this decade. In the last eight years, the Justice Department has brought roughly 15 obscenity cases that have not involved child pornography, compared with 75 during the Reagan and first Bush administrations, according to Jeffrey J. Douglas, chairman emeritus of the First Amendment Lawyers Association. (There have been hundreds involving child pornography.) Prosecutions at the state level have followed a similar arc.

The question of what constitutes obscenity relies on a three-part test established in a 1973 decision by the Supreme Court. Essential to the test has been whether the material in question is patently offensive or appeals to a prurient interest in sex  definitions that are based on “contemporary community standards.”

Lawyers in obscenity cases have tried to demonstrate community standards by, for example, showing the range of sexually explicit magazines and movies available locally. A better barometer, Mr. Douglas said, would be mail-order statistics, because they show what people consume in private. But that information is hard to obtain.

“All you had to go on is what was available for public consumption, and that was a very crude tool,” Mr. Douglas said. “The prospect of having measurement of Internet traffic brings a more objective component than we’ve ever seen before.”

In a federal obscenity case heard this month, Mr. Douglas defended another Florida pornographer. In the trial, Mr. Douglas set up a computer in the courtroom and did Internet searches for sexually explicit terms to show the jury that there were millions of Web pages discussing such material. He then searched for other topics, like the University of Florida quarterback Tim Tebow, to demonstrate that there were not nearly as many related Web sites.

The jury was evidently not swayed, as his client was convicted on all counts.

The case Mr. Walters is defending takes the tactic to another level. Rather than showing broad availability of sex-related Web sites, he is trying to show both accessibility and interest in the material within the jurisdiction of the First Circuit Court for Santa Rosa County, where the trial is taking place.

The search data he is using is available through a service called Google Trends (trends.google.com). It allows users to compare search trends in a given area, showing, for instance, that residents of Pensacola are more likely to search for sexual terms than some more wholesome ones.