Detectives finally knew for certain that the McStay family didn’t disappear over the border into Mexico when, in November 2013, a motorcyclist found their remains buried high in the Mojave Desert.

A sledgehammer was buried next to them. Their skulls and jaws were shattered and fractured. None were wearing shoes, and the woman wore no shirt, just a bra speckled with white paint. That was a sign to detectives that the four dead bodies might be those of Joseph and Summer McStay and their two toddlers — a case that had captivated a global news audience.

The family of four had just moved into their Southern California home when they vanished on the night of Feb. 4, 2010. The paint was still fresh on the walls, the corners bordered by blue painter’s tape and the floors covered in newspaper. Their beige five-story stucco home looked “camped in rather than lived in,” as one prosecutor would later put it. It seemed the McStays left without bothering to pack up. Two children’s bowls full of popcorn were left uneaten on the couch. Bananas and a carton of eggs were left rotting on the counter. Their dogs were left in the yard, their bank accounts untouched.

Charles "Chase" Merritt, left, reacts June 10 after being found guilty of four counts of first-degree murder of the McStay family. (Jennifer Cappuccio Maher/Pool/Orange County Register)

But for years, in the absence of evidence of foul play, everyone from investigators to strangers who heard about the case on mystery TV shows grew to believe that perhaps the McStays had disappeared on purpose. Some claimed to have sighted the family alive in Indiana or Montana or Baja California. Others thought the McStays slipped over the border into Mexico, their SUV having been found abandoned near the border.

The discovery of their bodies, however, silenced all the wild theories — and finally Charles “Chase” Merritt, the last man to see Joseph McStay alive, knew police were coming to see him.

“San Bernardino County have said they are going to start the investigation over from the beginning,” Merritt, 62, McStay’s business partner, told the Daily Mail shortly after the bodies were found, “and if they do, they’ll have to talk to me.”

On Monday, a jury convicted Merritt of bludgeoning the family to death after his business relationship with McStay fell apart, bringing the nearly decade-long saga to a close and making Merritt eligible for the death penalty.

In a trial that began in January and lasted more than 50 days, prosecutors presented heaps of circumstantial evidence they say tied Merritt to the slayings, including his cellphone records and banking records, but little to no physical evidence. Prosecutors argued Merritt was motivated by “greed and self-interest,” setting out to kill Joseph McStay, 40, after the businessman, who owned a company that sold water fountains, informed Merritt he owed him more than $42,000.

Merritt’s defense attorney, Rajan Maline, said the defense team was “shell shocked” by the conviction and intended to appeal.

“Based on the evidence, we did not expect this,” Maline said. “From our standpoint, our client is innocent. So the fight doesn’t stop here with us. We will continue to fight for our client, because we believe in his innocence.”

Before Merritt was even arrested in the case, he was asserting his innocence, claiming in his interview with the Daily Mail that McStay “was my best friend.”

The two had known each other for three years, he said. Merritt built decorative indoor waterfalls for McStay’s company, Earth Inspired Products. On the day the family disappeared, Merritt told police that he and Joseph McStay met for more than an hour at a Chick-fil-A to discuss an upcoming water-fountain project, according to testimony from the first detective to interview him, San Diego County Detective Troy Dugal.

Prosecutors claim there’s no evidence the meeting ever happened. Instead, they say, Merritt was plotting to kill him.

Three days earlier, McStay was on the brink of firing Merritt, and sent him an email asking for the $42,000 he owed him after botching a job, prosecutors said. Rather than pay up, prosecutors claim, Merritt wrote himself checks through the company’s online accounting site, QuickBooks — which they believe was the betrayal that severed their relationship for good.

At first, however, none of this was apparent to investigators intent on tracking down the missing family in mid-February 2010.

"The bottom line,” Dugal told the Los Angeles Times in 2011, “was that life was normal for the McStays up to Feb. 4, and on that day they just vanished.”

Theories about their possible escape to Mexico flourished as police revealed new details in the following days and months.

The family’s Isuzu Trooper had been spotted on surveillance pulling out of their driveway about 8 p.m. on Feb. 4 — only to be abandoned and towed from a shopping center parking lot on Feb. 8 in San Ysidro, Calif., just across the border from Mexico. A search warrant executed on the family’s computer uncovered recent Internet searches for “What documents do children need for traveling to Mexico?” A few months earlier, Summer, 43, ordered a Spanish-language education program, the Los Angeles Times reported in 2011.

Investigators scoured hours of grainy surveillance footage from the U.S. Customs and Border Protection port of entry, zooming in on the fuzzy faces of thousands of people waltzing into Mexico. They focused in on a family of four, the parents holding hands with two little boys — and decided it might have been the McStays and their kids, who were 3 and 4 years old. The San Diego Sheriff’s Department handed the case over to the FBI in April 2013, believing the family was out of the country.

But family members were skeptical. Would Joseph and Summer, who were in regular contact with their parents and siblings, really drop off the face of the earth without even leaving a note? And why, if they intended to disappear, would Joseph and Summer arrange for a painter to finish the job the following weekend, after they had already vanished?

“Why would my son, as smart as he was, take his family to a place that is so wildly dangerous right now?” Joseph’s father, Patrick McStay, told the Los Angeles Times in 2011.

The evidence finally placing Merritt at the scene of the crime was his cellphone data, prosecutors said. On the day the McStays disappeared, Merritt’s cellphone pinged off towers near the McStays’ home in Fallbrook. Later, it pinged off a cell tower in the Mojave Desert — near the site where the family was found buried. His DNA was also found on the steering wheel of the Isuzu Trooper, prosecutors said, although his defense attorneys maintained that was only because he had been in the car before and had contact with Joseph McStay.

“I wasn’t in the desert. I don’t know what to say about that,” Merritt claimed in an interview with police played for the jury.

Merritt had sought to clear his name and reputation ever since the bodies were discovered in the remote high desert. He claimed in an interview with the Daily Mail that McStay tried to call him at 8:28 p.m. the night of Feb. 4, but that he was watching a movie with his girlfriend and didn’t answer, a decision he claimed to regret. He said he kept trying to reach him in the days after McStay’s disappearance, and said he believed the killings were random, because “I don’t think any of his friends had anything to do with it,” as he told CNN in 2014.

But what he never denied was seeing McStay that day, before McStay and his family — who were killed because they were witnesses, prosecutors said — were buried in the desert.

He told CNN: “I am definitely the last person he saw."

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