David Marcus (aka David Stein) was reportedly close to Christa in the last years of her life. He had achieved a degree of infamy before they ever met, having been deemed "the second greatest pimp in NYC" by New York magazine, and arrested for imprisoning and assaulting a Playboy playmate in his L.A. home in 1972. Christa and Marcus also shared mutual friends in her last roommate Stephanie and Bernie Cornfeld, an international financier who lived in a luxurious L.A. mansion called Grayhall. Marcus spent a lot of time in the mansion as he excelled in procuring women for Cornfeld.
Death frequently followed in Marcus' wake.
When I was working to track down his whereabouts, I spoke to many people who knew him, including Rebecca Kaye, Cornfeld's secretary in the 70s. “[Marcus] was a Svengali, and everyone who got close to him got burned,” she told me. “He was evil.” Hollywood madam Heidi Fleiss shared with me that he would destroy young women with drugs and desperation. Another interview subject told me his sister was driven to suicide by Marcus.
Marcus was definitely on the radar of the cold casers during their investigation into Christa's murder, but they never managed to track him down (even though he was near their neck of the woods in Palm Springs the whole time). Marcus' brother told me that he had passed away in 2021, though I've been unable to verify this.