Charles "Chase" Merritt, 57, was ordered to be held without bail after a brief arraignment in San Bernardino County Superior Court.
"My oath to my client is that I'm going to do everything that I can to be able to help him in this case to specifically see if there isn't a way that with the tragedy that's taken place that that tragedy not extend to him, and not extend to his family also," defense attorney Robert Ponce said.
Merritt, a business associate of 40-year-old Joseph McStay, allegedly killed the family of four at their Fallbrook residence on Feb. 4, 2010, investigators said.
Joseph McStay, 43-year-old Summer McStay and their two sons, Gianni, 4, and Joey, 3, vanished without a trace in February 2010 shortly after moving to Fallbrook from Orange County. Their dogs were still in the backyard, and food was out on the counter.
Then on Nov. 11, 2013, the skeletal remains of the family of four were found in two shallow graves near Victorville, and the missing persons case immediately turned into a homicide investigation.
Merritt was taken into custody in Chatsworth after a traffic stop on Nov. 5 and booked at West Valley Detention Center.
VIDEO: Detectives arrest Charles Merritt in McStay family murder
The San Bernardino County Sheriff's Department has yet to release a possible motive, only that Merritt and McStay were business associates.
Howard Carroll and Dora Hammond say Merritt was a regular at the Cadillac Ranch in Victorville.
"He seemed pretty normal, mellow, easygoing guy -- the main thing he was out there was for shooting pool," Carroll said.
Summer McStay's mother appeared in court Wednesday, but refused to comment. Merritt's family also left quickly without speaking to the media.
Merritt is due back in court on Nov. 20 for a preliminary hearing.