Reporter:12 hours into the travis alexander homicide investigation and detectives had a lot of blood. And a lot of fingers pointed at jodi arias, travis' on anoff ex-girlfriend, who according to... See More
Reporter:12 hours into the travis alexander homicide investigation and detectives had a lot of blood. And a lot of fingers pointed at jodi arias, travis' on anoff ex-girlfriend, who according to friends with a full on stalker. But what detectives needed was proof she was there, ay' there about to find it in an unlikely hiding spot. Inside the washing machine. Still wet from the rinse cycle was travis' camera. On the data card, stored in the memory, time-stamped photos from the day travis was killed. On june 4th at 1:42, mr. Alexander was very much alive. Not only was he very much alive, he was involved in these photographs withan. Reporter: And who was that woman? One jodi arias, now brunette, posing in pig tails. The photos tell the story of an afternoon of prolonged passion. These were all taken between 1:00 and 2:00 p.M. That day. These photos were taken around 5:00. But less than two minutes after travis posed for this haunting picture, the camera captures this. A series of inadvertent photos, caused by a design flaw in the camera. In this one, the camera appears to be falling to the ground, a shot of the bathroom ceiling. And then this one -- a foot alongside travis' bloody body. They were able to retrieve these photos. And they somehow, miraculously, don't just tell the story of before and after, but during. And also provides, most importantly, a time frame when the actual crime occurred. Reporter: And there is another critical clue. A bloody palm print on a wall just down the hall from the bathroom where investigators believe travis was dragged back to the shower. Lab tests reveal that, too, belonged to jodi. And there's more. One week before the killing, a break-in at the home of arias' grandparents. One of the items missing? A .25 caliber gun. The same caliber used to shoot travis. Coincidence or criminal cunning on jodi's part? The burglar. The person who went in there. Right there. It's jodi arias. That's the burglar. And she needs a gun, and she needs a gun to kill travis alexander. Reporter: It was time for a chat with ms. Arias. Investigators headed to yreka, california, 1,000 miles from mesa, arizona, and arrested her outside her grandparents' home. They brought her here to the local sheriff's office. So you remember me? Of course I do. I've been working on travis' case ever since it happened. I know a lot of details. Okay. And I believe that you know some of these details. And I help us. I would love to help you in any way that I can. Okay. Reporter: When you watch the tapes of her interrogation, what strikes you most? She seems completely unflappable. And this goes to why she's such a good liar and potentially a good witness. Reporter: A good liar? Try casey anthony-caliber champion liar. Listen to this. Were you at travis' house on wednesday? Absolutely not. I was nowhere near mesa. I wasn't even close to him. What if I could show you proof you were there? Would that change your mind? I was not at travis' house. Was not. You were at travis' house. You guys had a sexual encounter, which -- there's pictures. And I know you know there's pictures, because I have them. She's very masterful at sounds very, very believable. And very innocent. If travis were here today, he would tell you that it wasn't me. She seems very genuine in what she's saying. And we know now it's a lie. I would never hurt travis. You did. I'm not guilty. I didn't hurt travis. If I hurt travis, if I killed travis, I would beg for the death penalty. Reporter: Getting nowhere, the detective shifts gears and hits jodi with the evidence. That's you. I wanted to cover you up because that's you -- all of you. Oh, that looks like me. But this one I don't know if I should show you, but it's just one of the photos that was taken by accident. It's your foot, jodi. That's travis. This is his bathroom. That is not my foot. Reporter: But this may be even tougher to explain. Should have at least done your makeup, jodi, gosh. Reporter: While jodi waited, she didn't seem like a normal person facing potential murder charges. She seemed -- well, off the wall. The next day, after a night in jail and a wardrobe change, jodi was back in the hot seat. But this time, she admitted she was at the house, where the killing happened. I was, like, right here on my knees and his bathtub is right here. Reporter: She told the detective that masked intruders broke in and attacked her and travis. I think I got knocked out but I don't think I was out long. There were two people there. One was a guy and one was a girl. What did they say? The girl wanted to kill me, too. Why didn't they? Reporter: She said she tried to help a badly injured travis. I came back this was, pushed her and he said, go to my neighbors, go to my neighbors, and he's like, I can't feel my legs. And they wouldn't let me by by him. Reporter: Police didn't believe it. So many inconsistencies. Reporter: But it turned out there were plenty of people that wanted to hear it, and jodi was more than happy to oblige. No jury is going to convict me. Why not? Because I'm innocent. And you can mark my words on that one. Reporter: One of the cameras jodi sat down before was ours. You have a mirror? Reporter: You are watching never before seen footage of jodi in 2008, just after her arrest. Born and raised in california. Reporter: Portraying herself as a family girl. I have a large family. Reporter: A loving girlfriend. He made me feel like a very beautiful person. On the inside. Reporter: And an innocent victim. All othe evidence, to me, is very compelling, but none of it proves that I committed a murder. If this were something that i could have done, itld be scary times, I think, spiritually and, thinking of what life beyond this. Reporter: What lines beyond is the answer to the ultimate question. Ladies and gentlemen, i understand you have reached a verdict. Reporter: Two stories. Which story do you want to believe? Reporter: Two minutes between an intimate moment and a stabbing frenzy. Gets a knife and stabs him in the chest. That's when it starts. Reporter: What really happened in that bathroom? That is almost certainly what killed him.
This transcript has been automatically generated and may not be 100% accurate.