Transcript for Chris McCowen's post-arrest police interview comes into question: Part 8
At the courthouse is actually a sculpture of Lemuel Shaw. It was Lemuel Shaw who formulated, more than anyone else, the doctrine of reasonable doubt. If these jurors think it is reasonable to believe that someone else might have done it, that's reasonable doubt and that's an acquittal for Chris Mccowen. The defense said that Christopher Mccowen's statements to the police could not be trusted. The statement is not worth the paper it's written on. Mccowen was spoken to for about six and a half hours. That interrogation was reduced to a 27-page report by state trooper Chris mason. The interview was about six hours. Is that right?? That's correct. I took notes. Now, six hours of talk translates more to 300 to 400 pages. They should have recorded him, at minimum audio recorded him, preferably video recorded him. Because it was too crucial a statement. Mr. Mccowen indicated, "I decline to have my interview electronically recorded." Apparently under Massachusetts law someone being interrogated can refuse to have it recorded. And I indicated to Mr. Mccowen that -- that the courts prefer that the interview be recorded to insure accuracy. But that it was his decision to make. Christopher Mcgowan says that he did not say the things that the investigators say he said and he says that he was under the influence of percocet, cocaine and marijuana. He doesn't even really remember giving the statement. He was completely wasted when he was taken into that police station. I know he wasn't comprehending what was going on. And there was testimony about his iq being 76, 78, 80. Just above mental retardation. Having an iq of 78 and being subjected to that kind of stressful, prolonged interview, makes him susceptible to manipulation. He has a personality as a lot of children do, where he, they wanna please their interviewer. They wanna please the adult in the room. Bob George wasn't just saying he didn't do it and they can't prove their case, he was saying that there are a lot of other, much more credible suspects out there. And Mccowen's attorney is raising other issues about the evidence in the case. There's no forensic evidence tying Christopher Mccowen to the scene, except the degraded semen in Christa Worthington's body. And skin cells on her breasts. The seminal fluid could have been on her body for three to five days. The physical evidence does not match up. There were no fingerprints. There were no footprints. They had palm prints that were unidentified, and they had unknown male DNA from three individuals under her fingernails. From the prosecution perspective, the key is not what other evidence they could've found or might've found. It's the evidence that they did find. It's his DNA at a scene he'd initially said he'd never been at. The most important evidence in the case that was ignored was there were blue and white fibers found in her vaginal area, which came from clothing. Did you conduct any testing on some trace material recovered from Christa Worthington's pubic area? Yes. From the pubic area, there was various colored fibers. Most of them were blue and white. Chris Mccowen was not alleged to have been wearing anything that was blue and white on the evening of the homicide. But he was with somebody who was wearing a blue and white sweater. And that was Jeremy Frazier. Reporter: Jeremy Frazier took the stand as a witness for the prosecution. Are you a member of any gang or group? No. Reporter: The defense is trying to portray Jeremy Frazier as this dark, shady, gang-affiliated young man who would be the type of person to commit a horrific crime. His demeanor, his presence -- he was arrogant. Did you kill Christa Worthington? No, I didn't. Reporter: Jeremy Frazier's getting on the stand and saying I wasn't at Christa Worthington's house. And did the police ask you where you had been that day? Yes. And did you remember? No. It was very clear that he claimed that he didn't remember anything. He couldn't recall anything. In fact, you didn't even remember where you had been after the juice bar the first time they talked to you, right? Yep, until they fed me pieces of information. Where I was that night. When you say feeding you pieces of information, who was feeding you pieces of information? The state police. Reporter: Jeremy Frazier is a prosecution witness who is now saying that the state police were feeding him information. Jeremy Frazier's testimony was like an early Christmas present for the defense. In all of the trials that I have covered, I don't remember a prosecution witness ever sending up red flags like Jeremy Frazier did. Jeremy Frazier admits that he was with Chris Mccowen earlier in the night, but he says that everybody split up. Chris went one way and he went another, and he stayed at Sean Mulvey's house, a friend of theirs. You can see them together at that juice bar on the video. Mulvey alibis Frazier. Jeremy was probably the most intoxicated out of everybody. So, I told him to come with me. Did Jeremy remain at your house? The whole night. Yes, he did. And there was an initial meeting with the police where you told them you basically didn't remember anything. Is that correct? Yeah. That was the first time on advice from my father. So, was that a lie? In the first statement, yes. And then he changed his story. He then suddenly provided an alibi for Jeremy Frazier on the night of. It doesn't take Sherlock Holmes to figure out that there's something shaky about that alibi. Reporter: But the police and prosecution were satisfied with Jeremy Frazier's alibi. The DNA at the crime scene does not match Jeremy Frazier. And so that suggests that the only person at Christa's home that night, is Chris Mccowan. Adding to the mystery was an incident that occurred the day before Christa's body was found. The car was coming down here, didn't even put on brakes. Reporter: Christa's neighbor, a guy named Girard Smith, says he saw a black vehicle speeding out of Christa's driveway. It went right out through here, and kept on going. It was clearly somebody that was trying to desperately get away from Christa's house, but why? ???
This transcript has been automatically generated and may not be 100% accurate.