Transcript for Ben Crump hopeful trial of Derek Chauvin will end in conviction
I don't know if you've seen anybody be killed but it's upsetting. Reporter: Far 4 days an off duty firefighter, a teenager -- It wasn't right. He was suffering. He was in pain. Reporter: A clerk in a convenience store, and others, have been recounting one moment last may seared in their minds, now embedded in the soul of America. -Less, he didn't move, he didn't speak, he didn't have no life in him no more. Oh my god. Reporter: Details graphic, emotions high, as witnesses for the prosecution take the stand in the trial against former Minneapolis police officer Derek chauvin. Chauvin, who worked for the Minneapolis police department for nearly 20 years, has been charged with second-degree unintentional murder, third degree and second degree manslaughter, accused of killing 46-year-old George Floyd during a police stop. The images of it forcing this country to confront the old and festering wounds of racial injustice. What do we want? Justice! When do we want it? Now! Reporter: For the first time the jury and the public seeing video of George Floyd in the minutes before the altercation unfolded. Chris martin, who worked at the convenience store, describing Floyd's demeanor. He seemed very friendly. Approachable. He was talkative. He seemed to just be having an average memorial day, just living his life. But he did seem high. Reporter: He says Floyd paid for a pack of cigarettes with a phony 20-dollar bill. The store manager called the police. Minutes later, martin is standing feet from Floyd, his hand on his head. What was going through your mind during that time period? Disbelief. And guilt. Why guilt? If I would have just not tooken the bill, this could have been avoided. I haven't got a gun, man! I'm going to die in here! Reporter: You can hear chauvin's voice. I've got to control this guy, it's a sizable guy. Looks like he's probably on something. Reporter: Darnellla Frasier, 17 at the time, seen here walking to the corner store with her 9-year-old cousin. Was there anything about the scene that you didn't want your cousin to see? Yes. What was that? A man terrified, scared, begging for his life. Reporter: She then turned on her phone and recorded the last nine minutes of George Floyd's life. That death, 10 months ago, leading to this moment. Jurors in two courts, an ongoing criminal trial in Minneapolis, the oer on the streets in the court of public opinion. Chauvin is in the courtroom, but America's on trial. This is huge. This is going to show everyone how this county and probably how this country views police violence against a specific community. Reporter: For George Floyd's family, the trial starting is the latest step in their journey for justice. Their week starting with a vigil at a church in the heart of Minneapolis. Among those in the chorus of support are two brothers, 51-year-old civil attorney Ben. I call him unc. A lot of people say, oh, that's your lawyer. But you can tell the difference when they're being business and when they're being personal. Why can't black people be for justice too? Why do we have to settle for half justice? One of the most telling things is when he was saying to the police officers, I'm not that type of guy. Almost saying, I'm a legitimate person. And I think that's every black person's testimony in America. Trying to convince America, I'm not what you think I am. Treat me at least as a human being. Reporter: Crump has become a constant presence at the forefront of America's current civil rights movement. His mission, making sure the names and faces of the victims remain seared in the public's conscience. His resume, more than 300 civil rights cases. We have to say trayvon Mike Brown in Ferguson, Missouri. Tamir rice in Cleveland, Ohio. Alton sterling. Eric Garner. The first "I can't breathe" case. I'm struck by the fact that not only can you recall their names like a good lawyer might, but you say it in the way in which a father would talk about his children. The reality is this. But by the grace of god, any one of them could have been our children. I know sometimes it's hard for our white brothers and sisters to fathom that. But I think most black parents, every day they wake up, they pray that it doesn't happen to my child. Reporter: For this father of three, it's hard for his cases not to get personal. His two adopted sons, chancellor and Marcus, around the same age as some of the young victims whose families he's had to represent. Growing up in lumberton, north Carolina, crump had to learn tough lessons himself. One of nine children raised in public housing by great grandmother Minnie. We would read the newspaper. Trying to guess and sound out the words together and figure out what they meant. But in reading those newspapers, it was showing me that there was a bigger world out there for me. Reporter: A world he thought beyond the cruelty he saw as a boy in the south. Had an uncle who was the first person in our family to go to college. Came back to see us in the projects. I guess the local police wanted to show him that even though he was a college boy, he was still black. They brutalized him in front of all of us. Huh. You're sitting here with me, but as you began to tell that story, it seemed you went someplace else. I thought about -- just my mother and my uncles and all the adults. Because I was a child. How helpless they were in that moment. Reporter: Crump swore he would never be helpless, so the law became his shield and his weapon of choice. Not simply defending his clients, but restoring their dignity. I learnt a long time ago that if you're going to represent marginalized people of color, you have to fight in two courts. First you have to fight in the court of public opinion. If you win there, then maybe you might get to fight in the court of law. Fair to say you use the law, but when possible, you use the media as well? Very fair. The court of public onion is far more powerful in some instances than the court of law. You've been called the Thurgood Marshall of this generation. How do you see yourself? I am still a disciple of Thurgood Marshall, who's my north star. He really -- as he said in his own words, they never meant for the constitution to be for us. But we're going to make it ours anyway. It's not enough to say that was wrong. You also have to engage in, educate, and empower people to know what their rights are. Reporter: Over the years, crump has secured historic civil settlements. And we are honored to stand here with the family of George Floyd. Reporter: Including $27 million from the city of Minneapolis for George Floyd's family, the largest pretrial settlement for a civil rights claim. It is my hope and belief that in a capitalistic society, if they keep having to pay these huge settlements and these huge verdicts, that it will be a deterrent for them to continue to shoot first and ask questions later. Reporter: Crump recalls the hundreds of police-related cases, only a few indictments and only four convictions. He hopes when it comes to this trial, it will be different. I believe in my heart he's going to be convicted. Now my heart has been broken before. But I believe that video helped change America. Doesn't it make you angry, though, that so many people have had to die and will die on that read to justice that you speak of? I think that George Floyd getting justice hopefully gives some measure of justice to all these other black people who were denied justice. Reporter: Judgment day is days away, evidence still being presented to the jury. Today the prosecution's first witness, Floyd's girlfriend, Courtney beatty Ross. Ross forthcoming about their struggles with opioid addiction. Classic story of how many people get addicted to opioids. We both suffered from chronic pain. The defense is going to argue it's the drugs in his system, that's what killed him. He's focusing on the cause of death being a cocktail of drugs. The prosecution's going to do the exact opposite and say, it wasn't enough to kill him, they're going to focus on the knee, the defense is going to focus on the drugs. Reporter: In the end, 12 jurors will decide the guilt or innocence of Derek chauvin, fairly or unfairly swaying the court of public opinion. The question for them and all of us, not on the jury sheet -- will their verdict help heal America? Or deepen her divide?
This transcript has been automatically generated and may not be 100% accurate.