The first man convicted in the murder of Amanda Knox's roommate testifed Monday that he believes she and her ex-boyfriend are guilty, an accusation that prompted the American student to say she was "shocked and anguished."

"He knows we weren't there," Knox said emotionally moments after her accuser, Rudy Hermann Guede, had left the courthouse.

The testimony by Guede, a 24-year-old immigrant from the Ivory Coast, was closely watched in the packed courtroom in Perugia. He had been called as a witness for the prosecution in the appeals trial of Knox and Raffaele Sollecito, her Italian ex-boyfriend and co-defendant.

Knox and Sollecito were convicted for the Nov. 1, 2007, slaying of British exchange student Meredith Kercher, whose body was found in a pool of blood in the apartment she and Knox shared in Perugia.

Prosecutors claimed in Knox's first trial that Guede, Knox and Sollecito killed Kercher in what had begun as a sexual game.

Taking the stand, Guede confirmed the contents of a letter he wrote to his lawyers last year, which ends with a direct accusation to Knox and Sollecito. In the March 2010 letter, which was read out loud in court, Guede wrote that he had nothing to do with the "horrible murder of the splendid and wonderful Meredith Kercher by Knox and Sollecito."

"This is a thought I've always had in my mind," Guede told the court Monday.

"It's not up to me to decide who killed Meredith Kercher," he added. "I've always said who was there that damned night in that house."

Guede is serving a 16-year-prison sentence for the murder. He was escorted in court by police in handcuffs.

Knox and Sollecito were convicted of sexual assault and murder in separate proceeding. She was sentenced to 26 years in prison, he to 25.

"Raffaele Sollecito, Guede and I have only been in the same place in a court," Knox said. "I'm shocked and anguished by these statements."

"I don't know what happened that night," Knox added, saying she wished she could have said that to Guede's face. She was only allowed to speak after Guede was escorted out.

Guede was called by the prosecution to counter testimony by a fellow inmate and convicted child killer who claimed Guede told him during recreation time that Knox and Sollecito had nothing to do with the killing.

On the stand, Guede denied talking to Mario Alessi about the case. The letter that was read in court had been written by Guede in order to deny Alessi's claims.

Like Knox and Sollecito, Guede has denied killing Kercher, but unlike them, he has admitted being at the crime scene the night of the murder. He sought a fast-track procedure and has already exhausted all levels of appeal.

Speaking at the opening of his appeals trial, Guede claimed he had heard Kercher and Knox argue minutes before the Briton was slain.

He said he was at the house with Kercher when he fell ill and went to the bathroom with his iPod. He heard Knox and Kercher argue over money, then heard a "very loud scream" coming from Kercher's bedroom, and rushed to it. There, he said, he saw an unidentified man who tried to attack him. Backing down into the hallway, Guede said he heard the man say "Let's go, there's a black man in the house."

Guede said he heard footsteps leaving the house and looked out of the window, where he saw a silhouette that he later identified as Knox's. He said he then tried to rescue Kercher, who was lying in a pool of blood after her throat was slit, taking her in his arms and trying to mop up the blood with towels. But he panicked and left the house.

Guede fled Italy, and was found and arrested in Germany about a month after the killing. His DNA confirmed sexual intercourse with Kercher, while fingerprints and other traces attest to his presence in the house.

Knox and Sollecito have maintained they were at Sollecito's house the night of the murder. Their defense lawyers claim Guede was the killer and acted alone.