The victim's name was (is?) Jolene Cranley-Evans, and she was the wife of the actor/stuntman-turned-politician Jock Cranley, whom some of you might recognize as the commentator for the Arena War. In the 1970s, when Jock and his wife were still living in Blaine County, he got a gig in Los Santos to become a stuntman; however, his wife disapproved of this, as they would have to move to Los Santos for the commute. In order to make sure he got the gig, Jock took his wife on a hiking trip up Mount Gordo, where he promptly pushed her off the cliff; the cops did arrest the guy, but he was able to get away with the murder due to a lack of evidence, and he was released immediately afterwards.
Couple of connected easter eggs in the game confirm it was a murder; for starters, that blood puddle that Jolene's floating over in the pic above? That's JOCK written in blood; if you approach her, Jolene will disappear and allow you to get a better look - identifying her murderer well after her death.
Also, there's a campsite down at the base of the mountain, normally occupied by several pedestrians; if you go down there at the correct time, around 4-5 AM or so, you'll hear her eventually falling and screaming all the way down.
It's also possible to hear the actual struggle between Jock and Jolene, with the latter begging the former not to kill her. Don't know how to trigger that dialogue, though; I think I heard it's supposed to play when you get near the ghost, but I don't know for sure.
Neat little easter egg, that's for certain.