Prosecutors overcame a lack of any scientific evidence to secure a conviction Monday of Ingmar Guandique in the killing of former federal intern Chandra Levy.

Guandique, 29, will be sentenced in February on two counts of first-degree felony murder, one related to her kidnapping and one related to attempted robbery. He could face up to life in prison without parole.

The Levy case was challenging from the start. There was no forensic evidence linking Guandique to the crime scene in Rock Creek Park, no murder weapon, no eyewitness and no definitive ruling from the medical examiner on what killed Levy. Numerous mistakes by police and forensic scientists further hampered the investigation.

But prosecutors offered a compelling theory of how Levy died nine years ago. They presented believable testimony from a former cellmate of Guandique's who said Guandique confessed to the attack and the gripping stories of two women who were attacked by Guandique in Rock Creek Park about the same time as Levy went missing in 2001.

Jurors said that was enough to reach a guilty verdict.

"I don't know that it was particularly difficult," said juror Linda Norton, an interior designer.

When asked about the lack of DNA and other science in the case, Norton said: "Well . . . there was a lot of evidence. . . .You know how much evidence there was, all kinds of evidence, and we were in a very small room with all of that evidence every day and we went through it in a very deliberate manner." She said the length of the deliberation was a direct result of the volume of that evidence.

The jury of nine women and three men reached its verdict after 31/2 days of deliberations.

Juror Sharae Bacon said the cellmate's testimony convinced her that Guandique killed Levy. "There were no holes in his testimony," she said.

Levy's mother, Susan Levy, let out a sigh and looked at Guandique as the verdict was read and the jurors were polled. Two of the jurors seemed to wipe away tears.

Guandique, 29, wearing a blue turtleneck and a gray sweater vest, listened through headphones that translated the verdict into Spanish. He stared straight ahead and had no visible reaction.

But as he was led from the courtroom, he ripped off the headphones and threw them onto the defense table.