At 17, Ryan Matthews was facing the death penalty. What mattered was the knowledge someone cared about his case

A good lawyer can change the experience of everyone involved in fraught and frightening legal situations. In 1999, as a young barrister, I found myself caught up in a trial involving the death penalty in Jefferson Parish, Louisiana. The jury had found 17-year-old Ryan Matthews guilty of first-degree murder and the public defenders were ill-prepared. We had barely two days in which to assemble and prepare witnesses, family members and clergy ? people that lawyers should have been working with for six months. In those two days, we helped them prepare their statements, readied them for cross-examination by a hostile district attorney, and counselled them on how they might persuade the jury to save the life of the person they loved.

It was the first time I had heard a jury return a verdict of the death penalty. It is one of the worst things I have ever witnessed. The jury shuffled in looking tired. They had listened to evidence until midnight the previous night. None of them looked at us or Ryan. I knew that was a bad sign. In less time than it takes to play a football match they had decided that a young man, whom they had never met or spoken to, should die. "And you are unanimous?" the judge asked.

"Yes," the foreman replied.

Ryan's mother Pauline bent over. "My son, my son," she murmured, unable to bring herself to look at the jury. I stood behind her, my hand running up and down her back. She didn't collapse: they didn't even see her cry, although perhaps they wanted to. Pauline had never doubted her son's innocence.

The jury and judge left, and the rest of us slowly broke down as the victim's family celebrated on the other side of the courtroom.

Ryan's trial lawyers shook their heads and started packing up their boxes. They had only met Ryan twice during their preparation for this murder trial. They never discussed the facts of his case with him, what he knew about the shooting, or asked him what he was doing that night. They didn't know that he had a half-brother in a wheelchair who had been shot in the back. They had never asked his father why he was testifying against his son, never been to the scene of the crime, never spoken to the eyewitnesses who couldn't identify anyone at the time of the shooting but managed to identify Ryan years later, never called the car salesman to confirm that the car window on the car that Ryan was in that night didn't open, never stressed to the jury the significance of the fact that the DNA in the ski mask worn by the killer was not Ryan's, never talked to the guy who'd been boasting in prison about killing a white guy in his store, never found out that the boastful guy was in prison for manslaughter, never found out that his DNA in that manslaughter case matched that inside the ski mask. In short, they never believed they were representing an innocent boy, though his innocence would later be proven.

Ryan had cane rows in his hair. He was insubordinate and stubborn. It was these traits, his insistence on dressing like a gangster, that in the public defender's eyes ensured he received the death penalty.

The public defenders may have done their job, but not their duty. It was their duty to get to know him, to be his mouthpiece, to tell his story, to protest his innocence in the same way that we would protest our own if we were falsely accused, it was their ethical duty to zealously represent him, to prove his innocence ? let alone preserve his existence ? yet they only met him twice.

I jumped over the dividing barrier in the courtroom and sat down beside him. "Ryan, you don't know me," I said. "I've been working with your mom and your family." He nodded and said: "Don't you worry about me, I'm all right." I wanted to scream: "No you're not, you're 17, you've been convicted and sentenced to death for a crime you didn't commit, you're the victim of a miscarriage of justice, you're the victim of a racist and segregated society." Instead I put my hand on his shoulder. "I've been telling your mom and your sister out there, while we were waiting for the verdict, that this isn't the end, this is the beginning. It is the beginning of the fight to prove your innocence and none of us are going to give up on that fight. It's not going to be easy and it's going to be hardest for you but in the end we will prove your innocence." Ryan smiled at me again. "I'm all right," he said calmly.

I asked a bailiff if his mother was allowed to talk to Ryan before they took him away. "When the courtroom's empty," he said nervously, indicating the departing victim's family. I motioned to Pauline. "They're going to allow you a little time with Ryan," I said, "when everyone's gone." She nodded. This would be the first time for two years that Pauline would be able to put her arms around her son. "Can you mind out for Monique? I can't be round her right now."

Outside the courtroom Monique, Ryan's sister, was freaking out in the corridor: screaming, slashing at her face, tearing pictures and notices off the wall. "Ma'am," said one of the bailiffs, "you better take her outside." Two of us managed to coerce her into the lift. When the door opened on the ground floor four deputies were waiting, handcuffs out and hands on holsters. "Ma'am, you're gonna have to come with us." They looked ready to lunge at Monique. "Please," I said, "just let her out of the building, please. Just give us a minute." They hesitated, giving us enough time for us to half-walk, half-carry her outside. I left her there with my colleague and went back in to collect Pauline.

I was a young and newly qualified lawyer. It was my first death-penalty trial. We had only had two days to prepare the case. I don't feel that I was equipped with any of the right tools to challenge or effectively help the lawyers in Ryan's case. What, I have asked myself in the years since, were we doing there? We had done nothing to change the outcome. Perhaps all we really did was make sure there was no grounds for appeal on grounds of poor representation.

I got the answer a few years later, sitting in the food court of a New Orleans shopping mall with Pauline. She had just emerged from a deep depression and wanted to talk to me. Pauline explained to me how lost she had felt throughout the trial, as if she were drowning and unable to swim. She knew that she knew she needed to be taking control, but she couldn't. She had been acting on instinct and her primary instinct was her own survival. She felt she was letting her son die because she didn't know what to do to help. "Then," she told me, "you guys showed up, it was if you were angels, I knew that God existed again and he had answered my prayers, for the first time since Ryan was arrested there were people who cared about us, who cared about my family, who cared about what was happening to my son in that courtroom, who cared whether he lived or died. It was such a relief just not to feel so alone."

I don't think I was capable of answering. We were, I'm sure, both thinking of Ryan, who at that moment was confined in a 6ft by 9ft cell.

What Pauline gave to me that day has st
ayed with me throughout my working life: an ability to understand the reason why I do my work, the benefit that it brings whatever the outcome ? whether someone is facing the death penalty or not. I hope that every young person I have represented and their family know that I care, and that is why I am there.

The years we spent fighting to establish Ryan's innocence all seemed lighter and more driven after that. It is hard, with hindsight, to remember how bad it was. We didn't know that it would all turn out OK, and that in April 2008 Ryan and I would walk down the aisle of the church together ? he the best man, and me the bridesmaid, at Monique's wedding.

? In 2006 Shauneen Lambe set up Just for Kids Law one of the charities that will benefit from the Guardian's Christmas appeal. It provides advocacy, assistance and support to children and young people between the ages of 10-21 who find themselves in difficulty. Read a 2008 interview with Shauneen.