The trial to solve the December 2000 murder of an 80-year-old woman will be decided by blood.

Victor Guzman, 39, is charged with the first degree murder of Severina Dolores Fernandez — a killing that was as mysterious as it was gruesome at the time of the crime. The only evidence connecting Guzman to the murder is a DNA sample taken from the scene.

In his opening statement on Tuesday, state prosecutor Scott Warfman described the scene in Fernandez’s otherwise tidy apartment in East Little Havana.

Police found her body in a puddle of blood on her bed, naked, with 58 stab wounds. Blood splatters stained the armrest of a chair, a couch cushion, the dresser, the window and the sink.

The trial began on an emotional note, with the prosecution calling Isabel Reyes, the victim’s niece.

Reyes spoke affectionately of her aunt and the routine that she kept every afternoon. Tia Lola, as Reyes called her, would go outside every day at 5 p.m. to get her newspaper, come upstairs, fold the paper to the crossword and get a bowl of sherbet to eat while she solved it.

When police found her body on the afternoon of Dec. 9, 2000, the tub of sherbet was still melting on the counter. Warfman showed the jury two graphic photos of the crime scene, which he said “looks like finger-painting, there’s so much blood.”

But not all of it came from the victim.

Fernandez managed to fight off her attacker enough to draw his blood, leaving behind DNA evidence that didn’t match existing police records.

Some two years later, the same DNA turned up in the rape of a 12-year-old girl in Miami Beach, but police had no idea whose DNA marked both heinous crimes.

Then in 2004, Guzman was arrested on charges of lewd conduct with a minor in an unrelated case and pleaded no contest. He was sentenced to two months in jail and 10 years probation. When he violated the terms of his probation, authorities realized he had never submitted a DNA sample as required of all sexual offenders. When police got his blood sample and compared it to a DNA database kept by the Florida Department of Law Enforcement, they matched him with the two previously unsolved crimes.

Last week, Guzman was convicted of attempted murder and lewd battery on a child in the case involving the 12-year-old girl. He was sentenced to 30 years.

On Tuesday, defense attorney Charles White asked jurors to “keep an open mind.” He said the state’s case rests on DNA evidence, and that evidence “is not going to show that anyone saw Mr. Guzman at the apartment.’’

If convicted, Guzman faces capital punishment, which would send the trial into a second phase in which the jury would recommend the death penalty or life in prison.