The mother of a Kansas University student killed in Costa Rica last year had her worst fears realized Sunday upon learning that the man she believed had repeatedly stabbed her daughter had been released from custody.

âÂÂIâÂÂve been afraid of this,â said Jeanette Stauffer of Topeka, the mother of Shannon Martin, a 23-year-old ecology and evolutionary biology student found dead May 13, 2001, near her host familyâÂÂs Golfito home.

Martin had suffered 15 stab wounds to the arm, abdomen and neck.

A judge on Friday released 38-year-old Luis Alberto Castro because of insufficient evidence. Castro still is prohibited from leaving the country and must appear before authorities every 15 days, according to prosecutor Erick Ramirez. A second suspect, 50-year-old Rafael Zumbado, was also cleared of murder charges because of lack of evidence but is being held on separate drug smuggling charges.

It was unclear whether prosecutors would appeal the ruling.

The two men were captured in July after Katia Vanesa Cruz Murillo, a female suspect in the case, tied them to the killing. She is still in custody, and her statement was the only evidence prosecutors had against the men.

Stauffer said in an interview Sunday evening that she was convinced Castro was the one who killed her daughter. Since the slaying, Stauffer has made three trips to Costa Rica to ensure the investigation moved forward.

âÂÂThere are people who know that he did it,â she said, but added that most were too frightened by Castro to come forward, even for the $50,000 reward.

She also said domestic law enforcement agencies and KU had taken too passive a role in gathering evidence in the case.

âÂÂIâÂÂm just so sick of the University of Kansas and the FBI not being concerned about this crime against my daughter,â she said.

University spokeswoman Lynn Bretz said KU had âÂÂput pressure on the highest levelsâ to see that the killers were brought to justice.

âÂÂOur heart goes out to ShannonâÂÂs family,â she said. âÂÂI think it might be a mischaracterization to say that we felt otherwise.âÂÂ

Although Martin was in Golfito for an individual research project, after her slaying KU performed an extensive safety audit on the area and in July canceled its study abroad program there.

StaufferâÂÂs lawyer, Pedro Irigonegaray, joined her in the assertion that the two men were involved in the case.

The Topeka lawyer said he would continue to work with the Costa Rican authorities to develop the case.

âÂÂI know from experience that these case are like marathons,â he said. âÂÂSooner or later we will get this case resolved.âÂÂ

And Stauffer said she was prepared to call the FBI and Costa Rican authorities.

âÂÂIâÂÂve been doing it for a year and a half, and IâÂÂm pretty much exhausted, but IâÂÂm not going to quit,â she said. âÂÂI wonâÂÂt quit.âÂÂ