The last man seen with Kristin Smart has been convicted of killing the college freshman, who vanished from a California campus 25 years ago.

Jurors have unanimously found Paul Flores guilty of first-degree murder, the San Luis Obispo Tribune has reported.

A jury in a separate trial found his father, Ruben Flores, not guilty of charges of being accessory to murder after the fact for allegedly helping to conceal the crime.

The conflicting verdicts were read moments apart in the same courtroom.

Ms Smart disappeared from California Polytechnic State University over Memorial Day weekend in 1996. Her remains were never found.

Earlier this year, US police said a podcaster’s efforts helped them catch Paul Flores.

Chris Lambert detoured from a music career to create a podcast, Your Own Backyard, about Ms Smart’s disappearance.

San Luis Obispo County Sheriff Ian Parkinson said Mr Lambert’s efforts helped bring forward witnesses who proved key to solving the case.

Prosecutors maintain Paul Flores, now 45, killed the 19-year-old during an attempted rape on May 25 1996 in his dorm room at Cal Poly, where both were first-year students. He was the last person seen with Ms Smart as he walked her home from an off-campus party where she became intoxicated.

His father, now 81, had been accused of helping to bury the slain student behind his home in the nearby community of Arroyo Grande and later digging up the remains and moving them.

The son’s defence lawyer, Robert Sanger, tried to pin the killing on someone else — saying Scott Peterson, who was later convicted at a sensational trial of killing his pregnant wife and the unborn child she was carrying — was also a Cal Poly student at the time.

During his closing arguments, Mr Sanger told jurors no attempted rape occurred and cast doubt on evidence from witnesses.

He also referred to forensic evidence offered by the prosecution as “junk science”.

“This case was not prosecuted for all these years because there’s no evidence,” Mr Sanger said. “It’s sad Kristin Smart disappeared, and she may have gone out on her own, but who knows?”

Paul Flores had long been considered a suspect in the killing. He had a black eye when investigators interviewed him. He told them he got it playing basketball with friends, who denied his account, according to court records. He later changed his story to say he bumped his head while working on his car.

However, the father and son were only arrested in 2021 after the case was revived.

Investigators conducted dozens of fruitless searches for Ms Smart’s body over two decades but in the past two years they turned their attention to Ruben Flores’s home about 12 miles south of Cal Poly in the community of Arroyo Grande.

Behind latticework beneath the deck of his large house on a dead end street, archaeologists working for police in March 2021 found a soil disturbance about the size of a casket and the presence of human blood, prosecutors said. The blood was too degraded to extract a DNA sample.

The trial was held in Salinas, 110 miles north of San Luis Obispo, after a judge granted a defence request to move it. The defence argued it was unlikely the defendants could receive a fair trial with so much much notoriety in the city of about 47,000 people.