It was a case that stumped investigators for years. A family of four, with two young boys, vanished mysteriously from their California home in 2010, leaving eggs to rot in the kitchen, their dogs without food and freshly made popcorn on the counter.

The family's skeletal remains were discovered three years later in a shallow grave in Victorville, nearly 100 miles north of their San Diego County home. Authorities did not make an arrest for another year.

At a preliminary hearing set to begin Tuesday, prosecutors are expected to reveal for the first time the evidence that led them to file murder charges against Charles "Chase" Merritt, the sole suspect in the case.

A judge previously denied a media request to unseal investigative filings, and authorities have said little about the killings of Joseph McStay, 40, his wife Summer, 43, and their sons, 4-year-old Gianni and 3-year-old Joseph Jr.

Merritt's name first surfaced in the investigation in 2011. He was a business associate of Joseph McStay, who designed and installed home water features. Merritt owned a waterfall company.

Authorities say the two met at a restaurant on the day the family is believed to have been killed. Merritt also told investigators that Joseph McStay's last cellphone call was to him.

When Merritt was arrested in November, authorities said they believed the family was killed in their Fallbrook home on the same day they disappeared — Feb. 4, 2010 — and died from blunt-force trauma.

But questions remained about a motive, why the entire family perished, and how the McStays' bodies wound up miles from their home and their abandoned car.

Merritt, 58, has pleaded not guilty and is representing himself. He is being held without bail.

In a jailhouse interview last year with KABC-TV, he said he was innocent and the evidence he had reviewed did not connect him to the gravesite or the scene of the killings.

The case initially baffled investigators and prompted San Diego County sheriff's deputies to launch what they called their most extensive missing persons search ever.

Four days after the family vanished, their white Isuzu Trooper was found at a San Diego shopping mall near Tijuana, Mexico. A dark surveillance video showed four people walking across the border.

Authorities initially thought they might have been the McStays but later discarded that theory.

Investigators said there were no signs of forced entry at the family home or in their SUV.

Nothing was missing from the home, and the couple's credit cards and tens of thousands of dollars in bank accounts were untouched.