Three federal judges have the task of deciding whether preventing or delaying adults' access to some constitutionally protected speech is an acceptable side effect of keeping online pornography away from children.

Closing arguments Thursday marked the end of nearly two weeks of testimony over the Children's Internet Protection Act, or CIPA, a law requiring public libraries receiving certain types of federal funding to install filtering software to prevent access to online smut. Under the law, libraries that don't install such software risk losing the federal funding.

The panel of judges are expected to rule on the case by early May to give libraries time to comply if the law is upheld and goes into effect as scheduled July 1. Any appeal of the panel's decision would go directly to the U.S. Supreme Court.

Attorneys for the plaintiffs — the American Library Association, a coalition of various public libraries and library patrons — said the evidence they presented makes shows the law is unenforceable, censors speech to adults as well as children, is overly vague and broad, and denies poor people without home computers the same full access to information as their wealthy neighbors.

"Ninety-three percent of the libraries in this country have chosen not to use blocking software on their computers. That's got to say something," said Chris Hansen, an attorney for the American Civil Liberties Union.

The government maintains that Internet porn is so pervasive that protections need to be in place to keep it away from the eyes of youngsters, and that the law simply calls for libraries to use the same kind of care in selecting online content as they do for books and magazines.

Justice Department attorney Rupa Bhattacharyya said filters aren't perfect but are efficient enough to support the mandates outlined in the statute, and added that CIPA does not discriminate based on viewpoints, only content.

"The statute ensures that federal subsidies are not used to allow access to this sort of material," she said.

CIPA also allows libraries to turn off filters for patrons engaged in "bona fide research," a concept Bhattacharyya didn't define, even when pressed by the judges. She said it's up to individual libraries to come up with their own definitions.

American Library Association lawyer Paul Smith, cited witness testimony that between 6 percent and 15 percent of Web sites that are blocked by filtering software are done so incorrectly. Some software can mistakenly brand Web sites on breast cancer, for example, as pornography.

Smith told the judges that filters entrusted with protecting children end up trampling on adults' First Amendment rights. The imperfect technology, combined with the dynamic nature of cyberspace, means filtering software will be "making new mistakes" as fast as the old ones are caught, he added.

"We have to decide how much is too much," said U.S. District Judge Harvey Bartle III, one of three judges who heard the case.

Third U.S. Circuit Chief Judge Edward R. Becker asked Smith how to protect patrons in places like the Greenville, S.C., public library, which "had become a virtual porn palace" because of unfiltered Web access was instituted, and in Tacoma, Wash., where the majority of attempts to access online porn were by visitors between the ages of 11 and 17. Librarians from both cities testified for the government.

"You've got terminals monopolized with hardcore pornography, you've got parents who are screaming about it, you've got 27-year-olds going over to young boys saying, 'Come over and look at this,"' Becker said. "What would you suggest these libraries do?"

Smith said libraries have "less restrictive alternatives" to blocking, like installing computer screens that don't allow others to see what the user is viewing and implementing strict usage policies.