- AJ prepares for the fight of his life. - Did this 16-year-old kill his parents? - It's impossible ` just totally impossible ` for AJ to have done something like that. - His grades had dropped. He's using drugs. He's fighting with his parents. This is a 16-year-old out of control. - RYAN SMITH: But there are so many pieces to this puzzle. That bizarre note ` 'I have been watching,' like something straight out of The Watcher; plus a break-in at one of the Armstrong gyms caught on tape. (GLASS SHATTERS) - They're very specifically looking for something. So we didn't know if the Armstrongs were involved in somethin' we didn't know about and it was revenge or debts... - RYAN SMITH: This other bombshell. (CAMERA SHUTTER CLICKS) - Maxine Adams went to police and says, 'I think Antonio Sr was part of a prostitution ring, 'and I think that he was targeted.' - MAXINE ON TAPE: That whole thing is just shady. - DETECTIVE: Do you think this is related to the homicide, or do you think it's just...? - Who could've done this? - Someone who has some severe mental health issues, someone who has access to the house, someone who knows where the gun is. (CAMERA SHUTTER CLICKS) (DRAMATIC NEWS STING) - Kia ora. Good evening, and a very warm welcome to 20/20. Tonight, we're bringing you the second part of the fascinating story of AJ Armstrong and his family. AJ was just 16 when his parents were fatally shot in their home. His mum, Dawn, died instantly; dad Antonio passed away in hospital. AJ was immediately the prime suspect for police, and after giving some conflicting answers under questioning, he was charged with both murders. Police, though, still need to find the physical evidence to tie AJ to the shocking crimes. (BROODING MUSIC) - Antonio and Dawn Armstrong were gunned down at point-blank range while they slept at their home in the Houston suburb of Bel Air. Now their 16-year-old son, AJ, who called 911 that night, stands accused of the unthinkable ` being the person who pulled the trigger. - Police charged AJ with capital murder as a juvenile and booked him into a juvenile detention facility. - The Armstrong family, they are struggling. This family is grieving. Meanwhile, Houston Police ` their work is just getting started. - The prosecutor had a meeting with the family members very early in this case, and we knew about it. And they said, 'Look, the evidence is gonna come back 'with gunshot residue on his hands. It's gonna come back, 'there's gonna be a DNA on him.' - I do remember hearing the DA tell us that if these results come back and they have no evidence, 'Hey, I'll be free 'to drop the case. Charges dismissed.' That didn't happen. - DETECTIVE ON TAPE: So you're 16? - AJ ON TAPE: Yes, sir. - Are you a junior or anything? - Yes, I'm a junior. - You are a junior? - Yes. - Junior? OK. - RICK DETOTO: AJ gave his statement because he felt like, 'I didn't have anything to hide.' - AJ: I've told you guys everything. Like, I mean, y'all` Like, all the tests you guys run will come back... - Yeah` I` No, I know. The prob` - ...with nothing` has nothing to do with me. - That's an innocent person saying, 'I didn't commit this crime, 'and you're not going to find evidence of it in my house.' - So, all those tests that police told RJ they were going to run come back, but they seem to confirm what AJ had been telling those detectives all along. - They` They didn't have gunshot residue on his hands. (UNEASY MUSIC) - MATT GUTMAN: Kayra Armstrong's hands, which were also tested for gunshot residue, came back clean, and detectives are surprised that there's no gunshot residue found anywhere on AJ. But there could be a simple explanation for that. - Person could've been wearing gloves. Person could've washed themselves thoroughly. Uh, there's many explanations. - It's a lucky find when you get it, but it doesn't mean that the crime didn't happen just because there isn't GSR. - Everything that they had access to was tested. There was no water in the sinks. No one used soap, so they can't claim he washed his hands. I specifically asked about that. 'Did you go into the shower, did you go to the sinks?' Nothing. - The gun at the scene was found on the kitchen counter next to a note. The note was on a piece of paper clearly torn out from a pad that was in the kitchen drawer. And when police test everything, there are no fingerprints of his on the gun. (UNEASY MUSIC) AJ's fingerprints are not on the notepad. They're not on the pen. They're not on the note that was left there. His fingerprints are nowhere. (SIRENS WAIL DISTANTLY) - And then there's the question of blood spatter. Rick Detoto actually says if AJ shot his parents at point-blank range, you'd expect there to be some blood on his clothing. - It's not always something that you expect to find. Sometimes you find it; sometimes you don't. Sometimes things are cleaned up. Sometimes it just depends on the location and the positioning of the body. - They didn't find any gloves with any evidence that he had worn them, or no bloody clothes in the washer or dryer... There's absolutely nothing that links him to any physical evidence in this case. - Where on earth did it go? - In order to try someone for murder, you know, put these charges to him and take away my nephew's life, then you have to put the gun in his hand. And they haven't done that. - Police say at this point they are not sure of a motive in the shooting. - And there's also the question of why AJ, who seems to be living a pretty typical teenage life, would want to murder his parents. It's all about the downward spiral of what's happening in AJ's life. - Prosecutors have a few theories. AJ was really struggling at Kincaid. He was... basically failing, and that's not acceptable for Dawn and Antonio. - What was goin' on? Why did you let your grades go south? - Uh, I was a 16-year-old kid. I had just got a car. So school kinda took a backseat. All I was worried about was football, I had a car... So, like, kinda the freedom got to me. - Because you were struggling at school, at Kincaid... - Yes, sir. - ...after your sophomore year, your parents decided to pull you out? - Yes, sir. - Were you upset? - I wasn't upset, because I knew that it was my fault, so I couldn't blame anyone. And I was ready to take that next step in my life and go to Lamar. - Lamar is a public school in Houston with a much more competitive football program. So authorities are wondering ` maybe being pulled out of his fancy private school where he's the star of the football team could be a motive for murder. - It turns out that AJ was faltering in many ways. He was smoking pot. He was missing curfew. - He's having his privileges taken away by his parents. It just paints a far different picture than what he explained to the police during his interview. - Could teenage drug use have had something to do with this? Now, according to the authorities, AJ's own grandmother, Miss Kay, brought that up on the night of the murders, telling investigators, unprompted, that, 'If AJ did it, it's because of the drugs.' - So let's talk about drugs. It's marijuana. Um, I don't think that makes you a murderer. - And so should we discount what his grandmother said about that? - Well, she was told before she made that comment, 'AJ's a suspect.' So that was her state of mind going into that question. And you talk to Miss Kay ` she's never believed he did it. Um, she stands by him 100%. - What makes me so sure? One, because I know my grandson. I know my family. We were close. It's impossible ` just totally impossible ` for AJ to had` have done something like that. - But if authorities had begun to think a picture of an out-of-control teenager willing to murder his parents was finally coming into focus, something was about to happen that would raise questions about that theory. (TENSE MUSIC) - A few weeks after the murders, one of the gyms that the Armstrongs owned was broken into. It was captured on surveillance video. - At this point, AJ was in custody in juvenile. - Two masked intruders bust in through the windows, coming inside... going through, looking, uh, for something specific. There was big-screen TVs in there. There was a lot of other equipment and things that they could have taken. But they left with just the computer. - And the person who did that, this defence attorney claims, could be a person of interest in the murders. - It's suspicious. We have a double homicide where you're accusing a 16-year-old of doing this. - That opened up a whole nother can of worms. Immediately, I start thinkin', 'Why are they coming for my family?' - When we come back ` that mysterious break-in, and then an entirely new theory about why the Armstrongs were killed. (DRAMATIC NEWS STING) (DRAMATIC NEWS STING) You're watching 20/20. Welcome back. AJ Armstrong's been charged with the murder of both his parents, and his legal team are scrambling for any answers other than it being the then-16-year-old who brutally killed his family. As we pick up the story, they're focused on an unusual break-in at the family business, and AJ recounts his struggles with being detained. All the time, though, his court case is looming ` and the question of his innocence or guilt. (UNEASY MUSIC) (MOTORBIKE SPEEDS PAST) - MATT GUTMAN: A few weeks after Dawn and Antonio Armstrong were murdered, surveillance footage captured masked men breaking into one of their gyms. And remember ` on the night of the murders, AJ said he saw a masked man in his house. So for the defence team, this was just too close to be a coincidence. - They're very specifically looking for something. So we didn't know if the Armstrongs were involved in something we didn't know about and it was revenge or debts or whatever, but... it further led me to believe that AJ was not involved in what happened. - This is an urban area. There are break-ins. It's` It's not an unusual occurrence. So I think it is a little far-fetched that the two are connected. - Those perpetrators were never caught, and AJ's defence team sees this as what they describe as 'investigators with tunnel vision 'refusing to adequately pursue leads outside of AJ'. - Well, my understanding is that it was very thoroughly investigated and there were no connections and no links whatsoever to this crime. (UNEASY MUSIC) - It's April 2017, and AJ has been in juvenile jail for eight months, and he spent Christmas there. It's basically his junior year of high school. - AJ: It was definitely... It was tough. Just not being around family, especially just at this time. It was just` It was a lot to deal with. - But then his case got transferred to adult court, where he was able to post bail. - Can you talk to us about how you're feeling? - AJ enters a plea of not guilty. - When AJ is finally released from custody, he goes to live with his grandmother. - This is my ankle monitor. It was part of my bond conditions was` I was bonded out. They placed me on house arrest, and... it's just been on since then. - GUTMAN: We visited AJ in 2019, and he told us what life on house arrest was like. - And it's frustrating. I look down, and it's just` It just reminds you of everything that I had to deal with in the case and all of that stuff. - He can go out into the backyard, he can go out into the street, but he cannot go past, like, the mailbox and stuff like that. (AUTOMATIC GUNFIRE ON TV) - I'm missing out on so much, and I'm seeing all my friends go on and do things with their life. I'm just stuck here. I try to stray away from social media as much as possible, just because it just shows me everything that everyone else is doing. It's` It's hard. - MATT GUTMAN: As both sides are preparing to go to trial, AJ's defence attorneys come up with what they describe as 'a huge bombshell'. - While they're preparing for trial, prosecutors send them a ton of electronic files, and AJ's attorneys are going through them, and they hear this recording... (CLICK!) ...and they say, 'Wait a second.' - I click on it; it's an interview with Maxine Adams at the Houston Police Department. - GUTMAN: Maxine Adams and her husband were friends of the Armstrong family. - Her husband at the time was good friends with Antonio. They, like, grew up together. Like, that was like a brother. - Maxine Adams went to police after the murders, and she says, 'I think Antonio Senior was part of a prostitution ring, 'and I think that he was targeted.' - She also made an allegation that Mr Armstrong, uh, increased his life insurance policy. - She gives very specific names, very specific phone numbers. At that point... I've never been that upset with a prosecutor, probably, in my career, because... 18 months since the interview until they disclosed it to us. - When they came and said that my son was involved in a prostitution ring, I was like, 'You` You can't be serious. That's not true. 'That's a lie.' What got me all worked up is the fact that they had this information December 2016. - It could have been the explanation that we were looking for, but we didn't get that opportunity. - Because of the delay, this young man continues to be on house arrest. Every time they come down here, they have to relive this. Every time they have to talk to the media, they have to relive this. We filed... legally to address the issue of them not disclosing and hiding exculpatory evidence, we filed a motion to dismiss. I knew that there was a 5% chance that the judge would grant that motion, but I wanted the judge to know. - GUTMAN: In their response to the motion to dismiss, the state admitted that they'd been aware of the Maxine Adams interview, and it was, in fact, not turned over for 18 months. But they argued that the remedy should be just more time for the defence to investigate. - Judge Kelli Johnson says, 'I wanna hear more about this.' She decides there needs to be a hearing. Maxine Adams comes to court; She testifies. - REPORTER: For the first time, we're hearing from Maxine Adams, who claims Antonio Armstrong Sr was involved in a prostitution ring. - Everything was looked into, and ultimately it was determined that none of it was relevant in this case. - Judge Johnson says, 'No, this isn't credible,' and she decides, 'This trial will move forward,' and AJ prepares for the fight of his life. (UNEASY MUSIC) 'Two years and nine months since the murder, 'and here we are in court.' The big question everyone has had is motive. - REPORTER: 19-year-old AJ Armstrong sipped on coffee before making his way inside court for his capital murder trial. (TENSE MUSIC) - On July 28th, the alarm was set in the home of Dawn and Antonio Armstrong. The alarm never went off. The killer didn't come from outside of the house. - Within minutes, the Houston Police Department decided he was a suspect in this case, and then they shaped this case to fit their opinion. - We don't have DNA. We don't have fingerprints. We don't have blood spatter. And so the real smoking gun for the prosecution shifts to the alarm system. - The alarm records showed that there had been no disruptions up until the time when AJ disarmed it to let law enforcement in. - That is virtually the end of the story for them. There's no ghost. There's no burglar. There's no nobody. - For the prosecutors, the alarm records are what's going to tell the jury what happened in the house that night. - COURTNEY FISCHER: There are sensors almost on every floor of the Armstrong house, and those sensors are important because, prosecutors say, it tracks the movement of the killer. - Prosecutors say that at about 1.09am, the motion detector on the second floor of the house, where Dawn and Antonio's bedroom was, goes off. They say that's AJ coming down the stairs to kill his parents. - What happened between 1.09, when the upstairs detectors went off, and 1.40, when the defendant said he heard shots? That's a long time to be able to... write a note, put a gun downstairs, change clothes ` whatever you need to do. - The defence, obviously, knew how important this 'star witness' the alarm system was going to be, so it had to create reasonable doubt about its ability to work and work well. - The defence has their own expert come and testify and study the alarm system, put together a video of how it worked. - This is the actual keypad that was used to arm the alarm system. - And he says the Armstrong alarm system is completely unreliable. - You'll notice that the door is, uh, slightly ajar. This did not stop the system from being armed. - The front door and the door from the garage were on the same loop, and if one of those was open, you could open the front door and the alarm wouldn't go off. - The front door can be opened... and closed without anything happening. - The other piece of evidence for the prosecution that really stuck with me was... the shot in the middle of AJ's bedroom floor. - This defendant is up in his bedroom with the gun, and he fires it through... the comforter. - The prosecutors believed that that, in fact, was premeditation. It was a test fire; he needed to make sure that he knew what he was doing. - 'How loud will it be? 'Will it wake my sister up?' - Regarding the bullet hole in the floor, he tells the police officers that he was showing his cousin how to shoot the weapon and they were just playing with it. You gotta remember he's 16 years old. - I'm glad this is in evidence. - Next up for prosecutors, something they think will show what was really going on with AJ in the months and weeks before the murders ` his text messages with his parents. - We start in, what, October 2015? 'Son, you can do this. 'We believe in you. You gotta bring up your grades. 'You can do this.' Then we get into January. 'You're lying to us.' February. 'You're starting to lie to us.' March, April, May ` it gets more sombre. - The text messages really paint the picture that this is a 16-year-old out of control. - Out of... a gazillion pages of text messages, they picked and presented to a jury only the things that, if you put it all together, would make AJ look like a liar or he had trouble with his parents. - SCOFFS: What was going on between AJ and his parents? Well, typical teenage stuff. - So, if AJ Armstrong didn't kill his parents, who did? The defence believes there is an alternate suspect. - REPORTER: AJ's defence team fired back. In a surprise move today, they pointed the finger at AJ's brother, Josh. - GUTMAN: Remember, Josh Armstrong, AJ's older brother, lived with his girlfriend just around the block from the family home. - Josh had access to the house just like AJ did. In fact, Josh showed up at the scene the night this happened. - The alarm was activated. The house was secure. There was no forced entry anywhere. So how could Josh have gotten in and done this and left? - Josh's hands were also tested for gunshot residue the night of the murder, but they came back clean. Houston Police ultimately ruled out Josh as a suspect. - But what they didn't know was Josh's psychiatric history that was coming. - The defence puts forth the fact that Josh Armstrong has been suffering from mental illness. - GUTMAN: The defence tried but was unable to submit Josh's medical records as evidence. So they call younger sister Kayra to testify about what they say was really going on in the Armstrong home. - Nothing could ever be said that would make me believe that AJ killed our parents. - She was in the house every day, day to day. She saw AJ, and she saw Josh. - FISCHER: Kayra said when Josh came home from college, he had changed. He'd lost a lot of weight. He started talking to himself. - I think when Joshua found out that Antonio wasn't his biological father, things changed. - I lived with Josh. I was with him every day. I know 120% in my mind that Josh would've never done this. - FISCHER: Hannah was with him that night. She says it was a normal night. He was playing video games. - I really wanted to just be... an alibi to Josh, but it kinda didn't work, because in court, they were like, 'Well, you were asleep. He could've left.' And... you just have to really kind of answer yes or no. And, I mean, yes, I was asleep, but... I'm... not a heavy sleeper. I would've... woken up. - Neither the prosecution nor the defence calls Josh to testify, and prosecutors insist that he is not a viable suspect. (TENSE MUSIC) - REPORTER: Closing arguments begin today in the AJ Armstrong murder trial. - You wanna know the answer? Here's the answer. The people in the house that took away his car, his money, that restricted his freedom to go see his girlfriend, they were killed. And you know what they took away from him that mattered the most to him? His status. - He's not a perfect kid. He never said he was an angel. But they're asking you to take that... and jump over to killing two people. Not just two people. His parents. - After four weeks, it's in the hands of 12 strangers ` did this teenager murder his parents? - Ladies and gentlemen, you now have all the evidence before you. - And no one knew what the jurors were gonna decide. - Yes. After all the theories and evidence, finally, it's time for a jury to make their choice on AJ's guilt. (DRAMATIC NEWS STING) (DRAMATIC NEWS STING) Welcome back to part two of the Armstrong story ` a Texas couple whose 16-year-old son is in court facing charges over their murders. A lack of physical evidence means both sides have had to build a case for motive. Was AJ so angry at his parents that he would kill them, or was his deteriorating relationship just normal teenage stuff? And, as he's always suggested, was there someone else involved? (SUSPENSEFUL MUSIC) - REPORTER: The jurors in the Armstrong murder trial are still deliberating. (BROODING MUSIC) - RICK DETOTO: As we waited and waited on that final day, the emotions and the pressure were overwhelming. - You know someone's life is hanging in the balance. - All rise for the jury. - We watch the jurors come in. They look exhausted and beat up. AJ stands, and immediately, it's the judge who starts talking. - The court finds it is improbable the jury can reach a verdict, and accordingly, because of that, the court declares a mistrial. - COURTNEY FISCHER: AJ just sits next to his grandmother and breaks down. - The jury was split eight to four. Eight felt he did do it; four felt he didn't. And that's the beauty of our system. It's a hung jury. It's frustrating to prosecutors, but the defence did its job in creating reasonable doubt. - We now know that there are people that do not believe the state's theory of the case, um, so we are gonna keep fighting for this young man as long as we have to. - Yeah, were we disappointed we didn't get an acquittal? Absolutely. But... the fact that he's getting to go home... is huge. (BROODING MUSIC) - Prosecutors released a statement, and it was short and it was direct, and they say Antonio Armstrong Jr ` AJ ` murdered two residents of Harris County and he will be tried again. - We read it. I-I wanted to know how fast could we get it done. If they said we could go next month, I'd be ready. My grandson needs to live his life. (BROODING MUSIC) - 2020 turns into 2021, and at this point, so much has changed in AJ's life. - I've been on house arrest for... today would make 1603 days. That's for you. - Has he been walking at all? (BABY GIGGLES) - No. - The biggest change in my life has become becoming a dad. You gotta let go. CHUCKLES: There we go. - Yay! (CLAPS) - 'I love being a dad.' It is a joy and happiness that I really have never felt before. It's just... once you have a kid of your own, you really do understand how much a child changes your life. - And Kate, the girlfriend, who has stood by AJ's side since the very beginning, is still with him. - He'll come if I have it. - Hey, Drix. Come here. - Mama. - We decided to do Hendrix Antonio to keep, uh, his dad's name going. - I mean, obviously, I would love for Hendrix to have been able to meet my parents. They would have loved seeing me grow and becoming a father. But I know they're up in Heaven and they're happy for me, and it's just` it's something I try not to think on for too long. - Is that good? - (GIGGLES, BABBLES) - I thank God for Hendrix. Amen. He is a blessing and an addition to the family. Now, at first I wasn't happy, and my family will tell you. I wasn't. Only because I was concerned about the outcome with AJ. I just didn't want a child to be born with all of this going on the way it was, not knowing the outcome. (SUSPENSEFUL MUSIC) - After three years of waiting, AJ's retrial is now officially scheduled to start in the fall of 2022, and the stakes are higher this time. A life sentence ` it weighs differently for a father. - You want some bottle? - He's grown up, become a man without his own father. Now he's facing the real possibility that his son will suffer that same future. - So how do you prepare for a second trial? - We're gonna have to start figuring out, you know, what we think the state is gonna improve on and how we can counter that. - Do you think it's possible to convince 12 jurors to acquit? - Absolutely. We do believe that. - Obviously, AJ's brother, Josh, was presented as an alternate suspect in that 2019 trial, and many are wondering if anything has changed in those family dynamics over the past three years. - Josh is Josh. Not... much to... really say about it. He's... He does his thing. We don't really... We don't see him much. - I don't know how Josh is really doing. I know they've been getting him medical help. In his right mind, he's sweet, loving... Good person. - It becomes clear that Josh Armstrong will once again be a major part of the defence's strategy when they file pre-trial motions claiming they have more evidence that demonstrates Josh's motive and mental health. - Josh's medical records were not allowed in the first trial, and this time, the defence says, 'You have to allow these in. 'Here's why ` we believe that this proves why he could be the killer.' - The prosecution remains steadfast that Josh has nothing to do with this case. - Now to a case we've been following for six years now ` - Mm. - AJ Armstrong is preparing to go on trial for the murder of his parents back in 2016. - I'm not scared. I'm trusting in God, and I'm believing that AJ's gonna be free after this. - REPORTER: The jury has been seated in the highly anticipated murder retrial for AJ Armstrong. - It's time for you to really get to know Josh Armstrong. - But this time around, prosecutors have something different in store for jurors as well ` new information extracted from AJ's cell phone. - The only 30 minutes all week that the defendant's not using his phone, his parents end up dead. (BROODING MUSIC) - Yes, it's time for AJ's second trial, and there's a whole new prosecution team. That's straight after this break. (DRAMATIC NEWS STING) (DRAMATIC NEWS STING) Welcome back. The second trial is beginning for AJ Armstrong, who was just 16 when his parents were shot and killed in their beds. His first trial ended in a mistrial after a divided jury could not decide on his guilt. Well, now he's facing the same accusations ` of murdering his parents because he was angry with them. And a lack of forensic evidence isn't holding back the prosecution, while the defence team continues to suggest his older brother is the real culprit. (TENSE MUSIC) - Six years after his parents were shot and killed in their home, AJ Armstrong is back on trial for their murder. - For the second trial, the defence is the same, but for the prosecution, the team is completely different. - This case is a parent's worst nightmare ` to come to the realisation that the person you brought into this world would end your life. - And for prosecutors, the alarm system is once again the star witness. But the defence continues to attack that evidence. - We know... what this is. This is a garbage can. The alarm records... are that ` garbage. They are garbage. - At the end of the day, although the defence is trying to say that there's all these glitches, AJ had to disarm it when he let the police in. It was activated and working just fine. - The alarm system is so important for prosecutors, but they don't just rely on that. Now they have software where they were able to extract more information ` because of new technology ` from AJ's cell phone. And it's not just who he's texting, what phone calls he's making, but now they're able to tell when his cell phone is plugged in when it's unplugged, and when the home screen is lit up. That's a big deal. (UNEASY MUSIC) - You know he is on his phone constantly. Then, at 1.02, he stops all cell phone activity. - Then, at 1.08, the phone is taken off of the charger. This is very important information. - There's only one reason why you unplug your phone ` it's because you're on the move. Why else would you unplug your phone, right? - One minute later, we know from the alarm records that the sensor on the second floor goes off. Then we know there's no other activity on that phone until AJ calls 911 at 1.40am. - But there's more. Because during that time, his phone is still locked, but the display is going on and off. There's two possibilities ` one, some push notification could be coming through; or two ` you're walking through a dark house and you're using the ambient lighting to go through the house. (UNSETTLING MUSIC) - This time around, the defence presents a case that goes all in on Josh Armstrong. They show jurors pages of his medical records, and AJ's attorney, Rick Detoto, reads jurors direct quotes from those medical records. - 'Josh is extremely psychotic, 'with command voices to hurt self 'and others. 'Brought to hospital by police with psychotic symptoms. 'Patient experienced watching the murder of both parents in 2016.' (SOMBRE MUSIC) - I feel that they feel... Josh's life has kind of, like, gone so downhill that there's no way for him to save himself, so let's just put it on him, when it's not fair at all. This is gonna stick with him for the rest of his life. - Once again, Josh Armstrong does not take the stand. - Go through those records and look at it. He says he witnessed his parents being murdered. That's what it means. - Prosecutors don't deny that Josh told doctors that he was there when his parents were killed, but they say Josh was there because he saw them being carried out on stretchers, wheeled into those ambulances. - The prosecution, they're very... careful and deliberate in pointing out that all of these medical records happen after the murder. - The prosecution argues his parents' murders acted as a catalyst, bringing on the symptoms of schizophrenia. - Josh definitely got super paranoid after. I've never experienced anybody being that paranoid. - They want you to believe mental illness means murder. (BROODING MUSIC) Are you offended? Are you offended? - I'm not picking on Josh cos he has mental illness. I'm picking on Josh because he said to multiple people, 'I witnessed my parents being murdered.' - Given the way he's been portrayed at both trials, we wanted to speak with Josh Armstrong, but he declined our request for an interview. At trial, prosecutors continue to insist he is not a suspect in this case. - Joshua Armstrong has been in and out of psychiatric centres, trying to get his life on track, and for six years, the person who is truly responsible for this crime has not yet been brought to justice. - REPORTER: All right, happening today ` we expect closing arguments in the murder retrial of AJ Armstrong. - Before the prosecution rests, John Jordan goes back to those text messages between AJ and his parents. He wants jurors to hear from one final voice ` Dawn Armstrong herself. - What I saw made my judgement. She says, 'I know... 'you left. 'The alarm doesn't lie. 'You lied.' - I think in that courtroom, you could've heard a pin drop when John Jordan put up that text message. - There are no words I can say that are more powerful... more appropriate... and more damning than that text message. - JUDGE: All right, ladies and gentlemen, you now have all the evidence in this case. Please retire the jury. - All rise for the jury. - CHRIS COLLINS: We thought we had done the best job that we possibly could have. We were just confident and putting our faith in the jury. (SUSPENSEFUL MUSIC) - COURTNEY FISCHER: After 17 hours of jurors deliberating, everyone gets called into the courtroom. - Today, jurors were once again unable to decide whether AJ Armstrong is in fact guilty in the 2016 murders of his parents. - It was deemed a mistrial. There was just this heavy sigh. Like, 'You've got to be kidding me. Again?' - At the first trial, it was eight to four in favour of guilt. This time around, the vote is eight to four again, but the majority voting not guilty. - It's been probably millions of dollars of expenses by the District Attorney's Office. It's time to let this young man go. - With another mistrial in the books, everybody's wondering what happened inside that jury room. - Tonight, we're also hearing from some of the jurors... - And a decision from prosecutors ` will they try AJ Armstrong for a third time, or will they let him go free? - Yes, another mistrial for AJ. And after the break ` the critical decision that will decide the rest of his life. (DRAMATIC NEWS STING) (DRAMATIC NEWS STING) Welcome back. Six years on from his parents' violent deaths, AJ Armstrong has had two hung juries unable to decide if he pulled the trigger when he was just 16. He's always maintained his innocence, and there's no fingerprints, no gunshot residue ` nothing physically linking him to the crimes. But he was the only other person in the house aside from his younger sister, and he did tell several conflicting stories about his actions. Well, now the prosecution team must decide their next steps. (BROODING MUSIC) - After jurors are unable to reach a verdict in Armstrong's retrial, one of them who thought he was guilty decided to speak out, although she asked that we not show her face. - JUROR: I feel everyone was moreso focused on the defence's... distractions, how I wanna put it, as far as Josh being a factor, and everyone just wasn't focusing on actual facts. Cos at one point, everyone said, 'Oh, we know he did it. 'We know he's not innocent, but we still have doubt.' - Just a month after the retrial, a stunning announcement from the District Attorney's Office. - Big developments in the AJ Armstrong case ` the District Attorney's Office confirms it will try AJ for a third time. - This means AJ Armstrong and his family will face a third trial. - And I've just grown a lot closer to that family just based on the period of years. (CHUCKLES) We've been through so much together. It would break my heart to have AJ behind those doors and go to prison. (DISTANT TRAFFIC HUMS) - You never imagine when you show up to a scene that you'll still be talking about this story six years later. (UNSETTLING MUSIC) We still don't really know what happened inside this house. We may never know. But somebody knows. (BROODING MUSIC) - I have thought about how we're gonna have to explain this to our son. It's a tragic situation, but it is our life, and this is his father. - I think about my parents every single day. There's not a moment, a second that goes by where they're not on my mind. They were my entire world. - My grandson ` he loved his mom and dad. His mom and dad loved him. You don't kill people you love. So love will always overpower evil, and love will always win, and the truth will always come out at the end. - There is no statute of limitations on justice, and it's my hope that the prosecutors will continue to try to seek justice for Dawn and for Antonio Sr, cos they deserve that. - You know you wanna be in it. - Even if we never find out who really killed my parents, I was still always remember them as my mom being my best friend and my dad just being the strong role model that he's always been. I will always keep that image in my head of them. - Well, that quest for justice did continue ` just last month, AJ finally faced his third trial for murdering his parents; this time, he was found guilty. He's been sentenced to life in prison with the possibility of parole after 40 years. AJ's now hired a new attorney and is appealing the verdict. The paperwork for that was filed only last week. And that is our show for tonight. Thank you so much for joining us. Until next Monday, kia ora. Nga mihi. ('20/20' THEME) Captions by Maeve Kelly. Captions were made with the support of NZ On Air.