A suspected serial killer will soon return to Clark County to be charged with the murder of a teen found dead in the 1970s.

KOIN-TV reports Warren Forrest has been behind bars since 1978, serving a life sentence for his conviction in the 1974 murder of Krista Kay Blake.

But he's suspected of abducting and killing a total of seven women and girls on both sides of the Columbia River. One of those girls was Martha Morrison.

Prosecutors in Clark County recently issued a first-degree murder warrant against Forrest for Morrison's killing.

Detectives believe Forrest's first victim was Jamie Rochelle Grissim. She disappeared after going to school in 1971 and has never been found; however, her school ID turned up along remote Doe Valley Road in Clark County.

Hunters found the bodies of Carol Valenzuela and Morrison nearby in 1974.

In an unexpected discovery revealed in 2017, Morrison's DNA was found on a dart gun that Forrest admitted to using to attack another woman.

Forrest has never admitted to other killings or if he knows where Grissim's body is hidden. But Grissim's sister Starr Lara hopes he can now be convinced to reveal what happened to Grissim while being prosecuted for Morrison's murder.

Forrest is expected to be transferred from the state penitentiary in Walla Walla to appear in Clark County court sometime next week.

— The Associated Press