CHESTER—Patti Lisk remains guardedly optimistic that the 1997 slayings of her two daughters will eventually be solved.

“I believe it will be solved when the time is right for my family and me,” Lisk said in an interview during an anti-violence conference dedicated to the memory of her daughters.

Kristin and Kati Lisk, 15 and 12, were abducted from their Spotsylvania County home after school on May 1, 1997. Their bodies were found five days later in the South Anna River in Hanover County. Authorities have not said how the girls died.

Authorities believe their killer is also responsible for the slaying of Sofia Silva, 16, who vanished from her front porch after school on Sept. 9, 1996. Her body was found five weeks later in a King George County creek.

Wednesday’s conference at John Tyler Community College focused on the marketing of murder through television shows, music and video games that glorify killing.

Nancy Ruhe, executive director of the Cincinnati-based National Organization of Parents of Murdered Children, cited several examples, from T-shirts sold during the O.J. Simpson trial to violent and bloody video games.

“We try to protect our children from drugs, alcohol, pornography tobacco. We don’t stop to think what it does when we show them murder after murder,” Ruhe told an audience of about 80 people, many relatives of slaying victims.

“And we have the audacity to ask, ’Why are children killing?”’

Mrs. Lisk told the Richmond Times-Dispatch that authorities keep her and her husband up to date on their case, which has had more than 11,000 leads.

But she tries not to get her hopes up with each new development.

“I try to temper it,” she said. “I do hope it happens, but I’m not vengeful about it.”