"48 Hours": First responder spoke up, became catalyst in murder case

(CBS) What really happened to Karina Ditto in the early hours of March 12, 2011? Did she injure herself from a fall down a flight of stairs or was it something more sinister?

Preview: 48 Hours: Shattered Dreams

For this week's 48 Hours, "Shattered Dreams," I interviewed San Diego Fire and Rescue first responder Lisa Challender. What struck me most about Challender was how she described her role as a first responder. "A lot of our job has to do with dealing with the public, responding on calls, and the other part of it is speaking for the victims," says Challender.

And "speaking for the victims" is what Challender did the night she and her crew answered a 911 call from David Ditto, who said his wife Karina had injured herself in a fall down the stairs in their home in the San Diego suburb of Mira Mesa. Challender says they were expecting to see wounds from a fall but when they got to the Ditto house, they found Karina lying on the floor in her own blood. Her heart had stopped.

Besides Karina's injuries, Challender found it odd Karina was not lying near the base of the stairs and she said there was no evidence to indicate a fall. Challender and the other first responders immediately sensed it was no accident and Ditto's story didn't add up. "I've probably seen thousands of falls," says Challender. "But they're not in cardiac arrest minutes after falling from a level of 10 or 12 carpeted stairs. I've never seen that before." Challender said the scene suggested there was a struggle and Karina was fighting for her life.

That's when the first responders called in police. After a thorough investigation and a report from the Medical Examiner, it was ruled that Karina died as a result of blunt force trauma and strangulation. David Ditto was charged with his wife's murder. Ditto emphatically denies the charge.

But Ditto may have never been charged with murdering Karina if Challender and the others didn't act on their suspicions. "Had we not spoken up" says Lisa, "the police would never have been involved. The police don't respond to falls. They don't. And so if we don't alert them that this is more than just a fall, they would never know."

Challender says she felt it was her "moral obligation" to speak up on behalf of Karina. "Even more so than my professional obligation to speak for her and to be her voice and say these things didn't happen as they're being said that they did. And-- and I think that that's really important and I think it's-- a huge part of our job. It doesn't happen very often, but when it's needed I believe that that's-- that's what we need to do."

At his trial Ditto insisted his wife's death was an accident. But would a jury believe him?

Written by 48 Hours Producer Deborah Grau