What it's like to go through a police interrogation

Former FBI agent and ABC News consultant Brad Garrett goes through the various tactics police use when interviewing suspects.
6:26 | 10/27/17

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Transcript for What it's like to go through a police interrogation
A two-way mirror. And that cop you don't want to mess with. You've been charged with two counts of domestic homicide. Reporter: Finding myself in the hot seat of a police interrogation, not where I thought my day would start. It's a process we all know from top shows like like "Law and order." What you did to her, you're lucky I didn't kick your teeth in. What I did, you should be so lucky someone does that to you. Reporter: "How to get away with murder." You're saying you didn't recognize this photo when it became public. Reporter: We wanted to find out what's on-screen drama, and what's real, from procedure and technique to coercion and false confession. Place your hands behind your back -- Reporter: This is where my journey started here in the back of a squad car. People are cuffed in the back seat, do they complain about it being uncomfortable? Yeah. It's uncomfortable. Reporter: Then it gets a little real. Step in there, face the wall. Put your right hand up on the wall. Hand up on the wall. Tag it. Now I'll ask you to remove your shoes. Reporter: Watching is former FBI agent Brad Garrett. We're going to uncuff you, we're going to take your fingerprints and photograph you. Reporter: Who says all of what I'm going through is part of the process of creating a relationship between cop and perp. The whole idea is to get you to feel in a very strange, stressed situation of you have some control because you can talk to us and maybe bargain on certain things. I'll have you stand with your back against the wall. Look forward right into this camera. Do people generally smile in these situations? Law enforcement doesn't control whether you're going to stay in jail and you get out on bond, whatever it might be. But the things that you do in the next few hours may have a profound effect as to what happens to you down the road. Reporter: We head into the interrogation. The space itself not an accident. Garrett says the rooms are often nondescript, private, small but not cramped. The key for me is that I need two things to start with. I need to be patient. And I need to be a good listener. Reporter: Luckily for me, I'm innocent and this is all a setup. But I'm starting to see how complex this process is. Interrogations are not an exact science. And there's plenty that can go wrong or right. Garrett shows me some techniques in action. In my mind, they got a gun -- Reporter: This from the interrogation of Michael Dunn, who shot and killed 17-year-old Jordan Davis in a 7-eleven parking lot in a dispute over loud music. This guy like goes down on the ground and comes up with something. I thought it was a shotgun. Reporter: Dunn tells the officers he feared for his life, and then they counter with the facts. Biggest problem we got, the first hurdle we got to get over, there is no weapon in that truck. So the detectives accurately say, Michael, you keep telling us in this video that you were scared for your life, that you thought they were going to kill you. How does them driving away and you firing eight shots at them, how does that protect you? Reporter: In another, detectives patiently listen to shocking details from serial killer Joseph Miller. Was she crying or screaming or anything? No, actually, she didn't scream or anything. I guess she was unconscious, I guess. So you hit her a few times just to make sure she was dead? Yeah. These detectives do a great job of walking him down the street. Not being judgmental. Not, oh my god, you did that to her! That's why it is so important in my view who you get to do interview and interrogation. Reporter: With that can come mistakes, including innocent people confessing to a crime they didn't commit. And as shocking as that sounds, one out of four people wrongfully convicted and later exonerated by DNA evidence have made a false confession or imcriticism nating statement. That typically happens when you have agents and detectives who just keep going at you and going at you. And people will sometimes give up that they have done something that they didn't do, because they want the pain and the anguish going on around them to go away. Reporter: Just last year, the topic on full display with the case of Brendan dassey in "Making a murderer." Come on, Brandon, be honest. You can do it. Just tell us the truth. I grabbed her, put her on the side, tied her up, put her outside and shot her. Why don't you draw where the blood stains there. Reporter: He spent ten years in prison convicted on murder and rape. Last year his legal team based an appeal that his confession was coerced. It's okay. Help us out. Where was the knife? Reporter: A federal magistrate went on to overturn dassey's conviction, later upheld by an appeals court, prompting the state to ask for another review. See? They get him to say anything that they want him to say. Reporter: Richard is one of the leading defense experts on interrogation tactics. He worked on the infamous case of the strat park five. I grabbed her arm. Grabbed one arm, grabbed her legs -- Reporter: Five teens who confessed in gruesome detail to attacking and raping a woman in the spring of 1989. Any time he would smack her, shut up, keep smacking her. Reporter: But these confessions were all false. They came to believe that they would only be able to minimize their punishment if they cooperated with the police. Reporter: These very real consequences, part of why Garrett says interrogations are so vital to the justice system. You can end up with false confessions because of the techniques you used. If the confessions are not done well, you can have innocent people going to prison for crimes they didn't commit, you can have guilty people getting off at trial because the confession's inadmissible? Exactly. It's a big deal. For a deeper dive into a true crime drama, check out our riveting "Nightline" series "A murder on orchard street" taking us inside a murder investigation alongside a New York City detective. The series is streaming now on abcnews.com and the chart-topping podcast is also available for download.

This transcript has been automatically generated and may not be 100% accurate.

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