Prosecutors are expected to claim a Southern California man used a sledgehammer to kill a family of four whose bodies were found years later in shallow desert graves, but there isn't a shred of physical evidence tying him to the crime scenes, a defense attorney said.

Charles "Chase" Merritt, 58, has a scheduled preliminary hearing Monday on charges that he murdered his business partner, Joseph McStay, the man's wife and their two young sons in their Fallbrook home in northern San Diego County.

Merritt has pleaded not guilty to quadruple murder. A judge will decide whether there is enough evidence to hold a trial.

The McStay family vanished in February 2010 and their remains were found in November 2013 about 100 miles away near Victorville in neighboring San Bernardino County. Merritt was arrested last November.

Authorities have not released details of the deaths of McStay, 40; his wife, Summer, 43; and their sons, 4-year-old Gianni and 3-year-old Joseph Jr.

The family's disappearance initially puzzled investigators who said there were no signs of forced entry at the home, nothing was missing, and the couple's credit cards and tens of thousands of dollars in bank accounts were untouched.

Prosecutors probably plan to argue that Merritt, who had a water fountain business with McStay, killed the family because he had written checks to himself on the business account and McStay had found out and planned to cut ties, defense attorney Jimmy Mettias told KCBS-TV (http://cbsloc.al/1f3Zk8L).

At the preliminary hearing, prosecutors likely will say the murder weapon was a 3-pound sledgehammer that was found in one of the graves, Mettias told the Daily Press of Victorville (http://bit.ly/1cMrFOX).

But there is no DNA, hair, blood or fingerprints tying his client to the McStay home or the graves, Mettias said.

"They'll rely on a couple of small things they believe would lead them to believe the murder happened at the home," Mettias told the newspaper. "The problem we've seen throughout this, there's not a shred of physical evidence that would even suggest that a quadruple homicide by bludgeoning people would have occurred inside the house."

Prosecutors intend to claim that Merritt painted the home to cover up the killings and there was paint found on the sledgehammer — but it doesn't match the type supposedly used to paint the house, the defense attorney said.

Prosecutors also plan to introduce cellphone records to establish Merritt's whereabouts, Mettias said.

Christopher Lee, a spokesman for the San Bernardino County district attorney's office, declined to comment Wednesday.

A defense team of four is representing Merritt, who previously represented himself.