Transcript for Police investigate timeline of Belinda Temple's murder: Part 4
The day of the murder, just hours after Belinda had been killed, David's family had reached out to a lawyer. I got a phone call fairly late in the evening that David's wife had been murdered and that they believed he was being treated as a suspect. Because it's almost always the husband, they're not doing an investigation. They're doing a witch hunt. I was driving at speeds in excess of 130 to get to David's parents' home, and I got there very quickly. I told him, either you're innocent and we have to have a full and complete investigation, or you did it and we need to make sure that nobody can figure out enough to prove it in court. I need to take one of those tracks. And he had no hesitation at all. He said, "I'm innocent. You do anything you have to do to make sure that these people are caught." My name is Steve wakowski with the Harris county sheriff's department. As the investigation unfolds, there are three key witnesses that investigators want to talk to, but they're just children. I am at the residence of Alexander and Linda Roberts. The Roberts family lived immediately behind the temple family, with the garage in between the two houses. Investigators learn that the Roberts brothers might have information that could help them pinpoint the time of death, which the medical examiner couldn't do. What these young men said was that they got off the bus and went home, and they had a snack, did a little homework, and they started watching "Dr. Dolittle." Good evening, doctor. While you were watching "Dr. Doolittle," did something happen? There was a noise, like, boom. Even though there were no eyewitnesses to Belinda temple's murder, arguably there were ear witnesses. I heard, like, this big boom, like, boom. What did you think the boom was at first? A firecracker. And then what did you think? Gunshot. With law enforcement, they picked the spot in the movie where they heard this noise, and that time was around 4:35. Why was that key for you, that they heard this noise at about 4:35? If they heard a gunshot at 4:35, David was at Brookshire brothers. Surveillance video actually captures David across town, nowhere near his house at a grocery store. Then there's one more video at 5:14, at a Home Depot. So we have these two surveillance videos where David is captured throughout the afternoon on camera. It's an airtight alibi. So investigators are now starting to think, "Who else could it be?" And, boom, literally, the boy next door is brought to their attention. I sent a letter to the prosecutor and said, "Look, man, I'm hearing a lot of rumors. You need to check out this neighborhood kid." Riley Joe Sanders. We call him Joe. He was a nice guy. He was a little nice guy. There's nothing bad to say about he liked to smoke weed and party. He lived next door to her, and he went to school at Katy high school, and she had him in some of her special Ed classes. It wasn't a secret that he was constantly missing school, doing other things but his academic work. Belinda temple complained to his parents about him skipping school, and he lost his driving privileges. You take a teenager's car and you might as well take their testicles. And it was because of the lady next door. It's pretty safe to say that Riley Joe could have had a grudge against Belinda temple, but is that a motive for murder? The day of the murder, Riley Joe Sanders was actually one of the students interviewed by the local news. I can't believe anything like this would ever happen to her. He gives an interview and tells reporters that he'd been at school all day, and come to find out, that wasn't true. He was the most interviewed and interrogated suspect out of everybody. Investigators looked at Riley Joe Sanders, they looked hard at him, but at the end of the day, there wasn't enough hard evidence that made him a more plausible suspect than her own husband. So they turn their attention back to David. So they talk to friends of Belinda and they learn that this wasn't the perfect marriage. Shortly after Evan's birth, things kind of started to turn south in the marriage of Belinda and David. He would call her fat, slap her on her butt and call her a fat -- From what you saw, how did Belinda react to that? She was hurt. She had some concerns about the time away from home that David was spending. She suspected that maybe something was going on. I think she was hoping that it was for good reasons that he wasn't coming home on time. How often did David temple talk to you about going to the happy hours? I would say, often. Where else would you go? Bars, strip clubs. Whose idea was it? Usually David's. At this point, the couples' relationship has taken a major turn for the worse. They didn't talk for six weeks and we were a little confused about that because I thought, how could this be, not talking to your husband for six weeks? But yet somehow they rekindled their relationship apparently. Because suddenly she's pregnant with another child. I can't explain relationships. She was so excited about this new baby coming, and she didn't feel like David was as excited. Boom, there's other reasons, other ulterior motives behind David temple's behavior. The proverbial other woman enters the picture.
This transcript has been automatically generated and may not be 100% accurate.