Golfito, Costa Rica ? Judges convicted two people of simple homicide and found a third person innocent on Monday in the killing of a Kansas University student.

Kattia Cruz, 28, and Luis Alberto Castro, 38, were found guilty of simple murder and sentenced to 15 years in prison for the killing of Shannon Martin, a 23-year-old student from Topeka.

6News video: Death threats do not deter Shannon Martin trial (11-20-03)Past stories

Martin was stabbed to death on May 13, 2001, after she left a nightclub in Golfito, 105 miles south of the Costa Rican capital of San Jose.

A third person accused in the killing, Rafael Zumbado Quesada, 48, was found innocent of all charges by the three-judge court.

Cruz and Castro were absolved of more serious charges of qualified homicide, which could have carried a sentence of more than 30 years. They received the maximum sentence for simple homicide.

Prosecutors and the family of Martin had asked judges to impose the maximum penalty of 35 years against all three.

During Monday’s closing arguments, the attorneys insisted that while some details remain fuzzy, there was enough evidence to prove guilt.

“We don’t have a crystal ball that tells us what each one was doing at the scene of the crime, but the evidence indeed has proven that the three participated in the actions,” said Juan Carlos Arce, an attorney for Martin’s family.

Asking for the maximum sentence, Arce and prosecutor Erick Martinez said that Martin had been stabbed 14 times and that witnesses had been threatened not to testify.

Martin was in the country to gather specimens for a biology project at the time of her death.