A computer expert yesterday told a County Council subcommittee that is considering legislation to block all pornographic material in Allegheny County's 44 public libraries that even the most sophisticated filters will let images through.

"Most filtering systems are very good at blocking texts and [specific Internet addresses]," said Dan Jude, chief executive officer of Security Software Systems, a Texas-based company. Unfortunately, he said, no technology is available to block sexually explicit graphics and photos.

Jude and several others attended a meeting yesterday of council's Public Safety Committee.

Members discussed legislation, authored by County Councilman Vince Gastgeb , that calls for the eiNetwork, which links the 44 public library systems of the Allegheny County Library Association, to use filters capable of blocking all pornographic or inappropriate material found on the Web.

The legislation was in response to a February incident at the Bethel Park Library in which a pair of 12-year-old girls sat down at a computer terminal to review homework. At the same time, a man sitting next to them viewed nude women wrestling .

The man, Scott Rickenbach, 38, was charged with disorderly conduct. He also was ordered to have a psychological evaluation, not to enter a public library or have harmful contact with children.

"The incident that occurred in the library is a public safety issue," Gastgeb said. "Unfortunately, those little girls grew up a little quicker than they needed to."

Speaking during yesterday's meeting, District Judge Robert C. Wyda, who charged Rickenbach, said Rickenbach had engaged in that type of behavior for a couple of years.

"The librarians knew it was going on, but they couldn't catch him," Wyda said.

Viewing pornographic material is not illegal for someone older than 17, and library staff can remove a filter when an adult patron makes such a request. It is illegal for a library patron to view certain material, such as child pornography.

Gastgeb wants to block all indecent material, like the Web site viewed at Bethel Park Library.

His resolution would deny county funding to the eiNetwork if the filters are not maintained.

Currently, the county does not provide any direct annual funds to the eiNetwork. Instead, about $2.3 million comes from the county's Regional Asset District, which, under state law, provides money for libraries and other cultural institutions using county sales tax revenue.

All libraries that accept federal funds already are required to block access to certain Web sites under the Children's Internet Protection Act, a federal law passed in 2000.

The Carnegie Library of Pittsburgh uses NetSweeper filtering software.

Marilyn Jenkins, executive director of ACLA, said the software is updated on a regular basis.

"The way the blocking system works is, it blocks text. If something slips through, it is reported."

"Every library has an Internet policy. We are constantly trying to identify ways to prevent this from happening," Cynthia Rechey, Mt. Lebanon public librarian, said at the meeting.

The committee plans to meet again next month to discuss the legislation.