Investigators: LA Homicide

It was one of the worst homicides in Los Angeles County in five years.

Four people from one family were found tortured and murdered at home. Among the dead was an 8-year-old girl who was sexually assaulted.

Who killed this family, and why?

Crime scene investigators with the Los Angeles Sheriff's Department crime lab were soon on the scene. Sgt. Larry Mitchell is in charge of the investigation, and 48 Hours was on the scene with him as he worked.

Correspondent Richard Schlesinger reports on a story that first aired last October.

He begins by looking for anything unusual at the crime scene: "You're pretty much looking for anything that you see that's out of place. Things that are out of place, that maybe someone grabbed. Maybe someone touched, to give you a fingerprint. Or maybe give you some DNA that can lead you to a suspect."

But even Mitchell finds it tough to stay focused on the job at hand when he gets his first look inside the Ruiz house.

"I haven't seen very many crime scenes as violent as this one. There's a lot of violence here," he says.

At this point, the sheriff's department knows one thing for sure. Sometime between Friday and Saturday morning, in this Los Angeles suburb, 38-year-old Miguel Ruiz, his wife Maritza Trejo, his grandmother Ana Luisa Martinez, and his 8-year-old daughter Jasmin Ruiz were murdered.

"They pretty much ransacked the house," says Mitchell. "We got blood everywhere, on the walls, on the floor. It looks as though they tried to clean the place up a little bit 'cause there is a mop and bucket there. Lot of work to do."

"I've never seen a scene like this," adds Det. Ray Peavy, a lieutenant in the homicide bureau. "This is incredibly brutal. Incredibly hard to take, really, even for somebody who sees this stuff every day."

"He was the best father any child could ever had, and the best brother any sister could ever have," says Ruiz. "I'm going to miss him."

But crime scene investigators know that almost all criminals make mistakes and leave evidence behind.

The L.A. County crime lab is one of the best equipped in the country, and with good reason. They investigate over 70,000 cases each year.

The crime lab pulls out all the stops on this one, photographing every piece of evidence, analyzing blood and fluids, examining the tiniest bits of evidence: DNA testing, fingerprint processing and identification.

At the crime scene, the investigators are still at it - combing every inch of the house. It is a painstakingly slow and meticulous process, making for a long day and an even longer night.

"In the real world, this is a very stressful job," says Mitchell. "You're dealing with a lot of trauma. You're dealing with innocent people who have been brutally murdered. You deal with the pressure of knowing that you only have one chance to process this scene and once you're done, you can't go back."

At 11:30 p.m. on Saturday, 12 hours after the investigation began, the bodies are finally removed from the house. But Mitchell and his team haven't made a dent in the mountain of evidence left behind by the Ruiz family killer.

Mitchell believes that whoever did this had investigators like him in mind: "That's something you wouldn't normally see at a crime scene. It makes you stop and think. Maybe that's why these things were done, to disguise a motive."

The identification team gathers fingerprint evidence and documents the scene. The biology team analyzes and interprets blood evidence.

Thirty hours into the investigation, one detail catches the eye of an investigator: a chair out of place. Investigators believe the chair may have been moved from the dining room into the bedroom.

Did the killer move the chair? If so, did he leave some trace behind? Using a gadget called an electrostatic dust lifter, investigators discover shoe prints.

"That shoe, if we find it, we can make a conclusive match with those marks," says one investigators.

With photos of the shoeprints in hand, Det. Peavy sends his homicide detectives to search the neighborhood.

In a house just around the corner, they find a suspect wearing a pair of shoes with soles similar to the prints lifted from the chair. The shoes are taken to the crime lab where shoeprint expert Bob Keil will examine them.

He is sure they are a match: "There is no doubt in my mind that these prints came from this pair of shoes, to the exclusion of all other shoes in the world."

That was good enough for detectives. Less than 48 hours after the murders were committed, they arrested 23 year-old Alfonso Morales.

"It did make the hair stand on the back of my neck," says Keil. "I knew at that point, I'm going to have a hand in this. And this person is going to have an answer."

When the crime scene investigators searched Morales' house, they turned up even more evidence: a large garbage can filled with items stolen from the crime scene, as well as a T-shirt possibly stained with blood.

Morales lived nearby and occasionally helped Miguel Ruiz with his computer business. Investigators think the two men had a falling out when Morales was told to stay away from Ruiz's daughters.

But as the investigators were working on the Ruiz case, other work was already piling up. "From Thursday afternoon, we had 17 homicides. Even for us, that's quite a run in such a short amount of time," says Mitchell.

Although tired, he and his team are ready: "Everybody in this unit is here because they want to be here and this is what they want to do. They love the challenge of getting calls, working these difficult scenes. They love the opportunity to put their skills to work. And we're fine. We're ready for the next one."