Columbia, SC (WLTX) - Richland County deputies say they've solved a 30-year-old murder case, and the suspect turns out to be a man who's already serving time for multiple killings.

Sheriff Leon Lott announced Wednesday murder charges against 53-year-old Phillip Johnson in the death of 34-year-old Patricia Ann Green.

Green, was found in a drainage ditch near May 10, 1987 near the entrance of McEntire Joint National Guard Base on Highway 378. Lott said she'd been shot in the upper body and then left in the culvert.

Ever since, her death had remained unsolved.

However, Lott says cold case investigators sent Green's clothing to the sheriff department's forensic lab. Specialists were recently able to match Johnson's DNA to the killing. He was already in state prison serving multiple life sentences for murder and other charges.

Lott says Johnson killed two women before Green, and after murdering her, when on to kill two others before he was finally caught. It's not believed there was any connection between the victims.

"He's a cold-blooded killer," Lott said.

Johnson's been behind bars since 1988.

Phillip Johnson 

Lott says his officers went to present the evidence to him, Johnson confessed, and provided in-depth details about the crime. They told Green's family on Monday that they'd finally found her killer.

"It's all about bringing justice to the victims and closure to the family," Lott said.