(PHILADELPHIA, PA) -- The U.S. government sought on Thursday to defend its bid to protect children from online pornography in public libraries, with testimony about Internet software that allows library patrons to view explicit text but not photos on the World Wide Web.

David Biek, main branch manager for the Tacoma Public Library in Washington State, told the judicial panel that such software could filter out objectionable photographs without hindering the free flow of information.

"Users can get to any Web site and retrieve the text-only version of the Web site. The text is not blocked," said Biek.

His library also provides patrons with an automated system for placing anonymous requests to unblock Web sites with redeeming social value, such as online sex manuals or portrayals of Michelangelo's nude masterpiece, David.

Those claims could prove key to the government's defense of the Children's Internet Protection Act or CIPA, which is facing a constitutional challenge in U.S. district court from plaintiffs led by the American Civil Liberties Union who claim it undermines free-speech rights enshrined in the U.S. Constitution.

Biek was the government's first witness after two days of plaintiff testimony critical of CIPA.

CIPA, the third attempt by Congress to control online smut, requires public libraries to install filtering software that blocks objectionable material on the World Wide Web or lose millions of dollars in federal subsidies for Internet access.

A special three-judge panel headed by Edward Becker, chief judge of the 3rd U.S. Circuit Court of Appeals is expected to rule on CIPA's constitutional merits by early May. Appeals would go directly to the U.S. Supreme Court.

*** Repeated Attempts by Congress ***

Signed into law in 2000 by then-President Bill Clinton, CIPA's effective date has been delayed until July. Advocates say CIPA provides the government's best shot yet at protecting youngsters from commercial pornographers who have proved relentless in their efforts to lure young online customers.

The first attempt by Congress to control online smut, the 1996 Communications Decency Act was thrown out by the Supreme Court as an infringement of free speech. A second, the 1998 Child Online Protection Act remains sidelined by a court injunction.

But critics view CIPA as an attempt by social conservatives to deny public access to Internet sites that deal with controversial subject matter, including homosexuality and abortion rights.

Witnesses called by a coalition of plaintiffs that includes libraries, library patrons and Web site operators have spent days attacking the limitations of filtering software, saying that it inevitably blocks benign sites protected by the U.S. Constitution.

But Biek testified the CyberPatrol filtering software system used at 10 Tacoma library branches did not block two plaintiff Web sites, SafeSex.com and the gay lifestyle site PlanetOut.com.

Biek said few Tacoma library patrons request Web pages that are filtered by blocking software, placing the rate at 0.5 percent to 0.6 percent of millions of Web page requests initiated on the library's computers each year.

He said the filtering software had proven 95 percent accurate in stopping access to Web material prohibited by the library system's policy.

Members of the judicial panel appeared to be impressed by the performance of the Tacoma system. But the judges also seemed skeptical about the ability of the system to perform well without the oversight of an experienced and sensitive administrator.

U.S. District Judge Harvey Bartle was quick to point out that while only one percent of the Web sites blocked by CyberPatrol in 2000 proved innocuous and therefore protected by the First Amendment, the actual number affected was about 1,500.