"I absolutely know their financials and their friends better than I know my own financials and my wife's friends," says DuGal, 49, a homicide investigator for the last three of his 15 years with the San Diego County Sheriff's Department.
Friday marked one year since the McStays disappeared from their home in Fallbrook - a small town north of San Diego known for its avocado orchards - and DuGal says he is no closer to cracking the case than he was the day that Joseph's brother called to report the family was missing.
Four days after the family vanished, their white Isuzu Trooper was parked at a San Diego shopping mall, just steps from Tijuana, Mexico. A dark surveillance video shows four people walking across the border that night, possibly the McStays.
What troubles the detective most is that he has no account of the four days before they crossed the border. Were they staying with friends? Were they at a hotel?
"I think it's likely that something bad has happened," says DuGal, who is on a second career after serving in the Navy.
Joseph, who was 40 when he disappeared, was a mild-mannered surfer who made friends easily. He ran a business from home designing and installing water fountains. He kept promises and paid bills on time.
In his spare time, he played soccer and hung out with buddies. He was close to a teenage son from a previous marriage who lives in the San Diego area.
Summer, who was 43 when she vanished, was more reserved. An avid shopper, she frequented Ross Dress for Less and had a penchant for fur and Ugg footwear.
She was a devoted stay-at-home mom to Gianni, who was 4, and Joseph Mateo, 3. She gave birth at home and wanted them home-schooled.
Born Lisa Virginia Aranda, Summer has taken several names during her life, which DuGal chalks up to an eccentric personality. Her sister, Tracy Russell, told him that Summer once suggested she change her name to Autumn.
Summer admired Italians, which may explain why she once took the surname Martelli. DuGal hasn't found anyone in her life with that name.
"Summer did not care for her Hispanic heritage," DuGal said. "Therefore, she assumed identities in the things she liked."
The couple dated a while and married in 2007. They left a small duplex in San Clemente, south of Los Angeles, after their boys were born and bought a home in Fallbrook. They moved in over Thanksgiving weekend in 2009 and were unpacked when they vanished barely two months later.
DuGal found no signs of forced entry when he arrived at their home Feb. 15, the day that Michael McStay called to report his brother missing. A computer search piqued the detective's interest.
Summer e-mailed a seller on Craigslist about Rosetta Stone software to learn Spanish and asked that it be delivered to Joseph at a soccer game. Joseph's friends remember seeing him shake hands with two men at a game Jan. 29, the day of the arranged sale.
Internet searches on Jan. 27 included queries on passport requirements for travel to Mexico and whether there was an age requirement for entering the country.
On Feb. 4, the day of the disappearance, Summer made her last cell phone call at 2:11 p.m. to a homeopathic medicine company, and an employee remembered it well. It came minutes after an Internet search for the word "Anger" on the company website.
"Summer was adamant that she wanted to purchase a medication called Anger," DuGal said. "They said, 'Ma'am, it doesn't exist.'"
A neighbor's surveillance tape shows the bottom of what looked like the McStay's Isuzu Trooper passing at 7:47 p.m.
Joseph's last cell phone call came at 8:28 p.m. to an employee, Charles Merritt, to follow up on a meeting earlier that day. Merritt told the detective that Joseph spoke calmly and strictly about business.
DuGal thinks the family left the home alone.
"I believe something occurred within those four walls between the four family members that made them leave in a hurry," he said. "It may have been good. It may have been bad. I don't know."
DuGal opened the back of the Isuzu at a towing yard and found a Pottery Barn Kids refrigerator and sink for a playhouse, with children's videos like "Franklin Goes to School" that were purchased at Ross Dress for Less.
The SUV was towed from a lot with a two-hour parking limit. Employees remembered keeping tabs on it.
DuGal says the border crossing surveillance tape appears to show the McStays. The woman is wearing fur and Ugg boots. The two children and man wear hats, as Joseph and his sons often did.
The FBI assures DuGal that the McStays are not living under witness protection. Neither Joseph nor Summer had criminal records or signs of financial problems.
DuGal believes the family would have sent word home by now if they were safe.
"We're a year into this," he said. "I want to find the family."