VANCOUVER, Wash. (KOIN) — Warren Forrest, the convicted killer suspected of being a serial killer from the 1970s, was arraigned Friday for the 1974 murder of Martha Morrison.

Forrest has been in prison since 1979 for one murder. Detectives have long suspected he killed 7 women and girls on both sides of the Columbia River but a lack of evidence held the investigations back.

But a DNA breakthrough linked Forrest to the killing of Morrison, who was 17.

He was arraigned Friday morning. The case continues.