The unsolved murder of 17-year-old Mary London remains a mystery 35 years later, and Sacramento police are still hoping to find out what happened to the disabled teen.London, a developmentally disabled Sacramento High School student, was reported missing when she did not show up for her ride after school on Jan. 14, 1981. She was last seen near the school about 3:30 p.m.According to officers, London's body was discovered the next day, near San Juan and Airport roads with multiple stab wounds. The motive for her murder is still unknown.Police are asking for the community's help in identifying a friend of London's named Darrell, who would be about 57 to 58 years old."One of our cold case detectives believe that maybe Darrell has some information as to where Mary was heading that night or who she was associated with," Sacramento Police Sgt. Bryce Heinlein said.Authorities said Darrell is not a suspect but they want to speak to him.Investigators have revisited this case over the years, attempting to identify the persons or persons involved in the murder."You know, these cases never go away," Heinlein said. "And these are the most horrific and tragic cases that we deal with."Anyone with information about this case is encouraged to contact the Sacramento Police Department at 916-808-5471. KCRA 3's Sharokina Shams contributed to this story.