A state appeals court in San Francisco on Tuesday upheld a jury's determination that a 14-year-old Pleasanton girl was murdered in 1984 by a then-16-year-old fellow high school student.

But the Court of Appeal reduced the conviction of Steven Carlson, now 48, from first-degree murder to second-degree murder and ordered a resentencing.

Tina Faelz, a freshman at Foothill High School, was killed with 44 stab wounds when on her way home from school on the afternoon of April 5,

1984. Her body was found in a drainage ditch adjacent to I-680, east of the high school. Carlson lived nearby.

The case was cold for more than two decades, but in 2011, authorities announced that DNA investigations begun in 2007 linked a spot of blood found on Faelz's purse to Carlson.

Carlson, who then had a criminal record that included convictions for drug crimes and a lewd act on a 13-year-old girl, was arrested and charged with the murder. He was tried as an adult.

An Alameda County Superior Court convicted Carlson of first-degree murder in 2014. He was sentenced to 26 years to life in prison.

Unless Carlson successfully appeals to the California Supreme Court, the case will now go back to Superior Court for resentencing for second-degree murder, which carries a possible term of 15 years to life in prison.

In its ruling on Carlson's appeal, a three-judge Court of Appeal panel said the conviction must be reduced to second-degree murder because prosecutors hadn't proved the element of premeditation and deliberate intent needed for a first-degree murder conviction.

The panel said prosecutors' main argument for premeditation was the number of the stab wounds, but noted the California Supreme court has said that brutality alone is not proof of premeditation.

It quoted a 1968 high court decision that said, "It is well established that the brutality of a killing cannot in itself support a finding that the killer acted with premeditation and deliberation."

Unless there is other evidence of premeditation, a brutal killing "is as consistent with a sudden, random 'explosion' of violence as with calculated murder," the high court said in another ruling cited by the appeals court.

The panel rejected several other claims in Carlson's appeal, including his argument that the jury should not have been shown portions of a

videotaped jailhouse interview of Carlson by two detectives in 2011. Carlson was serving a drug sentence at Santa Cruz County Jail at the time.