San Bernardino, California (CNN) The man accused of killing four members of the McStay family in 2010 will stand trial, a California judge ruled Monday.

Judge Michael A. Smith determined there was sufficient evidence to try Charles "Chase" Merritt on four counts of murder for the bludgeoning deaths of Joseph and Summer McStay and their two young boys.

Merritt has pleaded not guilty . He was a former business partner of Joseph McStay, who sold outdoor water displays over the Internet.

The 2010 disappearance of the McStays has been one of Southern California's most enduring mysteries.

Heartbreaking details of how the family died emerged at Monday's preliminary hearing for Merritt, who was arrested late last year.

One after another, half a dozen detectives and FBI agents took the witness stand in San Bernardino Superior Court to provide the details of the family's violent end.

They told how the McStays -- Joseph, Summer and their sons Gianni, 4, and Joseph Jr., 3 -- were bludgeoned to death with a sledgehammer and buried in shallow graves in the high desert outside Victorville, northeast of Los Angeles.

Charles "Chase" Merritt is charged with four counts of murder.

For a time after their disappearance, the McStays were believed to have taken off on an extended vacation to Mexico. But the details didn't add up: Eggs were left on a kitchen counter and the house was being renovated. The family dogs were left, tethered and unfed, in the backyard.

And then in November 2013, their skeletal remains were found in two shallow graves in the desert. None of the victims was wearing shoes, authorities testified. All died of blunt force trauma.

Summer and Gianni were found in "Grave B," as investigators dubbed it, along Interstate 15 near Victorville; her husband lay in "Grave A," along with the scattered bones of the younger boy, Joseph Jr.

Grave B also held what authorities say was the murder weapon: a 3-pound Stanley sledgehammer. Investigators believe it came from the family's home in Fallbrook in San Diego County.

Joseph and Summer's skulls had been smashed multiple times. The boys' skulls were fractured as well -- Gianni's as many as seven times, according to testimony.

Joseph had a broken leg and rib. He was tied with an extension cord and wrapped in a futon cover taken from the Fallbrook house, a detective testified.

The evidence heard so far seems to indicate the family was accosted and perhaps even bludgeoned to death at home. Signs of renovation work -- paint and new hardwood flooring -- were found in the open kitchen and family room.

Summer McStay wore no top when her body was unearthed, and her bra was spattered with paint. The paint color matched the paint found in the home, according to testimony. The sledge hammer contained smears of the same paint.

Merritt was among the first to raise the alert about the missing McStays. He told their family he couldn't reach McStay and helped a brother search the house.

Although Merritt denied he'd ever driven the family's Isuzu Trooper, his DNA was found on the steering wheel and gear shift. The truck was found abandoned near the Mexican border soon after the family disappeared.

Judge Smith also heard from an FBI agent who analyzed phone records. He found 27 calls between Merritt and Joseph McStay on February 4, 2010 -- the last day the family was seen alive.

Merritt called McStay five times the next day, but none the day after that, February 6. On that morning, Merritt's phone pinged off cell towers in the Victorville area, where the graves were unearthed three years later.

Prosecutors on Monday also began to home in on a possible motive: money.

A detective testified about several checks written to Merritt on McStay's business accounting software. They were written after the family disappeared but were backdated to February 4, 2010. The checks were printed but deleted from the software. They were deposited to an account Merritt set up on February 3.

Asked about the checks, Merritt offered no explanation or gave conflicting stories, a detective testified.

Merritt has previously spoken to the media about his relationship with the McStays and professed his innocence.

Prosecutors ended their case Monday by citing an interview Merritt gave CNN's Randi Kaye before his arrest, in which he said, "I am definitely the last person [Joseph McStay] saw."

In his ruling, the judge found the backdated checks and DNA in the Isuzu to be compelling evidence to hold Merritt for trial.

He also noted that in interviews with police after the McStays' disappearance, Merritt referred to the McStays in the past tense.

The cell phone pings near the grave sites on February 6 and tire tracks consistent with Merritt's Chevy pickup also support inference of his involvement in the crime, the judge found.