David Ditto claims wife died from fall down stairs, but was she murdered?

"48 Hours" probes case involving abuse, family secrets and ultimately, a charge of murder

Produced by Deborah Grau and Gayane Keshishyan
[This story first aired on Jan. 5 2013. It was updated on July 6.]

(CBS) MIRA MESA, Calif. -- It was the early hours of March 12, 2011, when David Ditto found the lifeless body of his wife, 38-year-old Karina, and called 911:

911 Operator: Hi. Medical 323, what's the address of your emergency?

David Ditto: 7723 Canyon Point Lane ... my wife hurt herself running down the stairs ... please send an ambulance.

911 Operator: How old is she?

David Ditto: Please send an ambulance.

911 Operator: I do not want you to hang up ...

When first responders arrived at the Ditto home in Mira Mesa, a San Diego suburb, an emotional David told them his Karina had somehow fallen down the stairs and struck her head on the tile floor.

"I started asking her, 'What's wrong, what's wrong, are you OK?' 'Honey, are you OK?" Ditto told "48 Hours" correspondent Maureen Maher. "She wasn't moving, wasn't talking. So I -- I grabbed her, and held her. Lifted her into my lap. And was -- was holding her, and trying to get her to come to and she didn't respond, or didn't move at all."

Karina was rushed to the hospital, unable to breath on her own. For two days, Ditto and his family stood vigil as she clung to life.

"I was told that first day that she was brain dead," he explained in tears. "And then it was -- it was almost impossible that she would ever recover. Then, you know, the next doctor or nurse -- the next doctor would tell me, 'You know, there's-- it's still the same situation. There's -- she's not -- she's not gonna recover.'"

"It was really hard. I think at first it was just so hard for him to believe. They had their lives planned ahead. And it was just so hard to accept that this actually was happening," said Ditto's mother, Pat Doughty.

Doughty couldn't believe what had happened to Karina, the beautiful young woman who had captured her son's heart 20 years ago.

"This was the girl. This was the one that -- that was going to be his wife," she said.

It was the summer of 1993. Ditto was on college break, vacationing in Mexico. On his way to Cabo San Lucas, he stopped in the tranquil resort town of La Paz.

"I stopped to have lunch on the waterfront and I was parked in my car. Saw a pretty lady with pretty eyes and a beautiful smile. And she caught my eye," he said.

Karina was a shy 20-year-old.

"She'd smiled at me once or twice and I got up the nerve to go over and talk with her," Ditto told Maher.

"Would you describe it as love at first sight?" Maher asked.

"As close to love at first sight as you can get, I believe, yeah," he replied.

"When she was about 8 or 9 years old she'd say that she wanted to date an American," said Karina's mother, Silvia Benitez.

Benitez, the owner of a beauty salon in Mexico, knew her daughter was instantly smitten with David Ditto. She, however, was not.

"At first I didn't trust him," she told Maher. Asked why, Benitez replied, "He was too good looking and I said no, it's not possible for him to fall in love with a person like my little girl. And I asked him, 'Why her? She's Mexican and has different customs.'"

Karina spoke no English and David Ditto spoke little Spanish, but often, love has its own language. The two sparked up a long distance love affair through phone calls and letters and within a year, they married.

They first had a civil wedding in La Paz with Karina's family and then a traditional ceremony in San Diego with David's family.

"My stepdad, Bill, walked Karina down the aisle since her dad wasn't here to walk her down the aisle, and that was really special," said Ditto's sister, Maggie Cascio.

Cascio was one of Karina's bridesmaids.

"It was a beautiful wedding, it really was. The pictures -- when I look at them now, you know, I think, 'Oh, Karina, so young. My brother was so young.' I remember he had cut his hair, I think, probably, to please Karina's parents or her family more," she recalled with a laugh.

Newly married at the tender age of 21, Karina left her family, and all that was familiar, behind to start a new life with her new husband.

"I really respected the choice that she made to come up here, leave all her family, come to a new country where you don't speak the language. Not familiar with the culture," said Cascio.

Asked how Karina adjusted to life in the U.S., Ditto told Maher, "There was some difficulty. It was completely different. She was, you know, nervous and like a stranger in a strange land."

While going to school to learn English, the newlywed was completely dependent on her husband.

"He helped her a lot and kind of guided her at the beginning," Doughty explained.

Karina devoted herself to learning everything she could about life in America. She was particularly devoted to building her life with her husband.

"Karina really wanted to be a mother. That's something that she knew almost her whole life that she wanted to be a mom. And she was really good at it," said Ditto.

In 1996, they had their first child, a son. A few years later, their daughter was born.

As the couple was starting their family, Ditto was also starting his career. He took a job as a lab researcher at the University of California, San Diego.

"We were, you know, financially, just kind of starting off," Ditto explained. "... it was a little bit of a struggle. Didn't have a lot of money, but we had, you know, enough to pay the bills and, you know, have -- have food and -- and everything."

It seemed Karina was actually living the life she had always dreamed of as a little girl in Mexico ... from the perfect husband to the perfect home that David Ditto spent years saving up for.

"They had great plans for this place," Doughty explained walking through the home. "She wanted this house. She wanted this house. And David, you know, made every effort to get this house for them. And they did."

"They were just, you know, the ideal family and everybody -- everybody thought so. And just, you know, thought, 'What a wonderful family,'" added Cascio.

But appearances can be deceiving, as revealed in Karina's letters to her mother.

"... Sometimes I don't know why I married him," she wrote. "I'm in despair ..."

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