A number of sources do suggest that very thing:
Death to Pigs, by Hendrickson pg501
Bugliosi interview by Merrick, 12-15-71
Bugliosi: "I'm the one that put Manson inside the gates of the Tate residence. I put him in there, not on the night of the murders, but a couple of nights earlier."
Manson's Right Hand Man Speaks Out by Charles "Tex" Watson c. 2012 pg43
It's believed that Manson was at the house looking for Terry the night before the murders and was offended by the new occupants.
www.mansonblog.com/2016/07/does-hour-or-three-make-difference.html
Grimtraveller said... "Back in 2005 on Col Scott's site, someone called GLH said that he'd spoken with Tex the month before and this is what Tex had told him "Manson had been to Cielo the night BEFORE the murders". I debated that with him, saying I'd heard that Manson had been there in March '69. He stood firm on his claim that Manson was there on August 7th (in the evening). ...and Manson was agitated the next day"
Jay Sebring’s business partner Jim Markham:
"I believe Manson had gone up to the house” — Polanski was away shooting a movie — “and Manson wanted to sell cocaine and marijuana,” he says. “He showed Jay and Wojciech the product. They were going to buy some of it, but the two of them beat him up at the gate. The next night, Manson sent the Family up [to kill them].”
truthontatelabianca.com/threads/true-detective-1970.2881/
Beausoleil: "He(Charlie) had been over near his [Melcher's] house and, as he said, he checked out the wires, telephone wires and the electric gates and exits from that property."
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Wait... wasn't Charlie down in San Diego County on that date, bringing Stephanie Schram down to her sister's house in Jamul and having dinner there, and then sleeping on the lawn of the residence of one of Stephanie's friends? Well, that is what Bugliosi claimed. But what was that based on?
Not Charlie. He admitted going down to Jamul but didn't put a date on it.
Not Schram. She couldn't remember the date:
Helter Skelter, pg368
"Stephanie was a bit vague when it came to dates. She "thought" the day they returned to Spahn Ranch was Friday, August 8, but she wasn't sure."
Not that traffic ticket Charlie got from the Highway Patrol near Oceanside on the way down. It's never been made public.
Not Stephanie Schram's sister, identified only as "Mrs. Hartman," who allegedly claimed that Charlie told her that "people were going to be slaughtered, they'll be lying on their lawns dead." Her interview was never released.
Not Stephanie's 'friends' in San Diego on whose lawn Manson and Schram allegedly slept on, the night of Aug 7 to the morning of Aug 8. There's no evidence they were ever identified.
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Though of course Schram never said anything about Charlie stopping by Cielo Dr. in the time she was with him, from her meeting him near Esalen to when they allegedly returned to Spahn, "arriving there about two in the afternoon" on Aug 8, in Bugliosi's version.
But Schram claimed it was Aug 5 when she first came to Spahn with Charlie. They had dinner there, and then in the evening drove off the ranch, but only for a couple of blocks before Charlie pulled over and they slept in the bakery truck that night. The next day, which would have been Aug 6 if Schram is right, they drove down to San Diego, spent the night, returning to Los Angeles on what would have been Aug 7. Note that during his trial Tex claimed he saw Charlie at Spahn the next morning, on Aug 8. There are now enough gaps in the timeline to make a trip to Cielo the night before very possible.
So why didn't Bugliosi use evidence of this alleged visit by Charlie up to Cielo the night before, at the trial? It would have been very incriminating to Charlie, whether the visit was to do a drug deal with Voytek, as per Markham, or to do a reconnaissance, as per Beausoleil. The only realistic scenario is that Bugliosi could not have entered this evidence without revealing the source, which might refer to the house being under surveillance before the murders, as Doris Tate claimed.
Submitted by Starviego. Thank You Starviego.