SAN DIEGO — The defendant in a decades-old, National City cold case murder has been sentenced after pleading guilty earlier this year, San Diego County District Attorney Summer Stephan’s office announced Friday.

On June 7, Carlin Cornett, 70, was sentenced to five years-to-life in prison for the 1974 murder of Christy Bryant, a former Marine and 7-Eleven clerk.

According to Stephan’s office, Bryant was working the overnight shift at the Highland Avenue location of the convivence store in National City on July 31, when she was attacked by Cornett in the backroom. She was stabbed more than 30 times and was pronounced dead on the scene.

Investigators at the time discovered additional unidentified blood on the scene.

According to Stephan’s office, Cornett had cut himself during the struggle with the knife, leaving a trail of blood as he fled the store. But, the evidence ended up becoming a dead end, given technology constraints of the time.

The case went cold for nearly 50 years — up until National City investigators turned to new genetic genealogy technology to identify the blood found on the scene, collaborating with the Cold Homicide and Research Genealogy Effort (CHARGE).

The blood was ultimately traced to Cornett, who pleaded guilty to second-degree murder earlier this year on April 26. In 1974, the punishment for the crime was five years to life in prison, according to the DA.

“When a murder is unsolved for decades, it takes an enormous toll on the victim’s loved ones, but now the family of Christy Bryant have a measure of justice after many years of mourning their loss,” DA Stephan said in a press release. “I am grateful to our Cold Case Unit and detectives in the National City Police Department who worked tirelessly on this case until it was solved, and the killer was brought to justice.”