WASHINGTON -- While in prison, the man charged with murdering Washington intern Chandra Levy wrote a penpal admitting that he was involved in a crime that involved a "dead girl," a witness testified Tuesday, though her memory of the letter came under scrutiny in cross-examination.

Ingmar Guandique, 29, a Salvadoran immigrant, is accused of murdering and attempting to sexually assault Levy back in 2001. Levy's disappearance became a national sensation at the time after she was romantically linked with then-Rep. Gary Condit, D-Calif. He was once the main suspect, but police no longer believe he was involved.

Prosecutors have very little physical evidence linking Guandique to the crime, so a series of purported confessions that Guandique made to fellow inmates and others are a crucial aspect of the trial.

On Tuesday, jurors heard from Maria Mendez, 48, of Miami, who has a hobby of corresponding with prison inmates.

Mendez testified that Guandique wrote to her out of the blue in 2003, after getting her address from another inmate. Guandique at the time was serving a 10-year prison sentence for assaulting female joggers in 2001 in Rock Creek Park -- the same place where Levy's remains were found a year later.

Mendez said she requires all inmates to be honest with her and tell her why they're in prison if they want to correspond with her. Guandique wrote a lengthy letter in response that referred to a "dead girl" in a park. Mendez said the letter made her uneasy and she ended her penpal relationship.

The letter itself has since been discarded, Mendez said. On cross-examination, she admitted that she could not remember whether Guandique wrote that he had committed a crime involving a dead girl or whether he had been accused of killing a girl. "I don't remember the exact word he used," Mendez said.

She spoke with Guandique once on the phone as well, and told him that a crime involving a dead woman made her nervous. Guandique did not respond, according to testimony. Jurors heard the a recording of the call in Spanish, and received an English translation, but that translation was not made public.

Mendez's testimony came a day after Condit took the stand and denied involvement in Levy's disappearance and death. But Condit adamantly refused to answer questions about whether he had a sexual relationship with Levy, claiming he was entitled to a level of privacy as a matter of "common decency."

The defense argues that Guandique has been made a scapegoat for a botched investigation.