Peter Pringle and Sunny Jacobs have a lot of things in common, as most couples do. They both love yoga, meditation and swimming, vegetarian food and living in the countryside.

But the couple, who were married in New York just over a year ago, have something else in common that connects them in a profound way. Before they met, Sunny and Peter faced the death penalty for separate yet eerily similar crimes. In 1976, Sunny was placed on death row in Florida for the murder of two police officers. Four years later, in Dublin, Peter was sentenced to death for the murder of two officers of the Garda Síochána, the Irish police force.

Both lost huge chunks of their life in prison: Sunny served 17 years, Peter 15. However, both were victims of wrongful convictions, their lives on the line for crimes they did not commit. But they were eventually exonerated and now, at least, they are free. Together, they have rebuilt their lives.

Sunny and Peter met in 1998 when Sunny, who started campaigning against the death penalty soon after she was released, travelled to Ireland to speak at Amnesty International events. Peter went to one of her talks in a pub in Galway. He sat in the front row while she told her story and sobbed quietly, moved by her suffering but also by the realisation that here was someone else who knew what it was like to be sentenced to death for something they hadn't done.

"Since I'd been released, I'd never met anyone else who'd been through this kind of trauma," says Peter, who is now 74 (he was 41 when he was convicted). "I was deeply touched by her story and I just had to talk to her. There was this spiritual connection there."

Sunny was 28 when her life changed. She was travelling with her boyfriend, Jesse Tafero, and her two children, Eric, nine, and Christina, 10 months. Their car had broken down in Florida and they were trying to get home to North Carolina.

Someone Jesse knew, Walter Rhodes, agreed to drive them. Sunny thought Rhodes was "creepy". She fell asleep with the children in the back seat, but was startled awake by a policeman knocking on the window. The next thing she knew, chaos ensued and gunfire opened. She was arrested. Her children were taken away.

Rhodes negotiated a plea bargain with the state, claiming Jesse and Sunny had pulled the triggers, in exchange for a life sentence. Sunny was put in solitary confinement for five years, awaiting execution. Her cell was minuscule at 6ft by 9ft, and she spent days pacing back and forth. She began to practise yoga. In her book, Stolen Time, she writes: "Hopelessness just didn't appeal to me … they can keep me here but what goes on within the confines of these walls is mine to create. They cannot imprison my soul!"

Her sentence was eventually reduced to life, but Jesse was executed in horrific circumstances. The electric chair malfunctioned and it took him 13 and a half minutes to die. Flames reportedly shot out of his head.

After Jesse's execution, Rhodes confessed he had fired the fatal shots confirming both Jesse's and Sunny's long-maintained innocence. Sunny was freed in 1992. But it was a difficult freedom to adjust to. By this time, she was 45.

"I had to learn how to do things all over again," says Sunny, who is now 65 and looks notably frail for her age because of a chronic back problem. "I had to learn how to make a living, be a mother and simply be a person again. It was very difficult, but at the same time I wanted to get past it. I wouldn't say my experience haunts me, but it's always there. Everyone gets challenged in life and you can either spend the rest of your life looking backwards, or you can make a decision to keep going. That's the choice I made."

While Sunny was in prison, her parents, who looked after the children, died in a plane crash. Her children were older and for most of their lives, their mother had been in jail. Life on the outside was completely different. Rebuilding her life and bonding with her children were her priorities. After having lost Jesse, falling in love again was the last thing on her mind.

"I was attached to Jesse for a very long time, even after his death. It took me about three years to finally let him go," she says. "I'd given up on meeting anyone. I just accepted that not everyone was meant to have a partner. But then I met Peter."

After their initial meeting in Galway, Sunny went back to the US and they began to write to each other and talk on the phone. "It was spiritual and special," says Sunny. "We'd talk about forgiveness. We'd talk about healing."

She came back to Ireland to be with Peter. Seven years ago, on the shortest day of the year, they walked down to the shore and exchanged vows. Then in 2011, they had an official marriage ceremony in New York.

Sunny Jacobs and Peter Pringle at their wedding ceremony in New York, November 2011. Among the guests are actors Brooke Shields, left, and next to her Marlo Thomas and Amy Irving, all of whom played Sunny in The Exonerated, a play about death row prisoners later proved innocent. Photograph: John Lamparski/WireImage

At more than 6ft tall and well-built, Peter towers protectively over Sunny, placing a large gentle hand on her back to support her as she walks. A former fisherman, his face is rugged, his beard and hair thick and snowy white.

Peter was one of the last people in Ireland to be sentenced to death in 1980. He says most people's first reaction is that they can't believe Ireland had the death penalty – capital punishment was only abolished in 1990, with a constitutional ban on the death penalty introduced in 2002.

He was arrested after two police officers, Henry Byrne and John Morley, were shot. Byrne and Morley were chasing three armed, masked men who had robbed a bank and were fleeing the crime scene. The Garda car collided with the getaway vehicle and the robbers opened fire. In Ireland, the murders caused national outrage.

Peter maintained he was never a part of it. At the time, he was separated from the mother of his children and was on his way to see her to negotiate spending more time with his four children.

But at the final court hearing, the judge declared that all three men, including Peter were to be sentenced to "death by execution". His lawyer broke down in tears after the sentence was passed. The prosecution maintained that wool fibres from a jumper detectives say Peter wore when he was arrested placed him in the robber's getaway car. And police statements presented as evidence stated that he had made a 'voluntary verbal admission', which Peter had always denied. A key witness, a police officer, identified another man as the third culprit, not Peter.

Peter was already known to the Garda because he had been involved with the IRA in his youth and arrested because of it in his early 20s.

But that experience was nothing compared to what it was like in the death cell, Peter says. He spent months in isolation for 23 hours a day. Conditions were harsh; the cell was cramped, with no natural light and a plastic potty in lieu of a toilet. He overheard his jailers talking about his hanging.

"When I was in that cell, I realised that until they killed me, I was still my own person. They couldn't imprison my mind, my spirit or my heart. That somehow gave me relief and I promised myself I would live in prison in the best way possible," he says. "My biggest fear was not dying, but that I would die without dignity. I didn't want to let myself go in front of the jailers."

Peter began to prepare for death, practising meditation and exercising when he could. "I was afraid I'd let myself and my children down. The hardest part was being isolated from them. I was very worried about what it would mean for them to have their father hanged. Every visit from them was heartwrenching. I was flattened by the pain in their eyes."

But two weeks before Peter's execution date, set for June 1981, the prison governor told him that his sentence had been commuted – instead of the death penalty, he now faced 40 years in jail. Peter's immediate reaction of relief was quickly followed by despair. "I couldn't face 40 years in prison with no chance of getting out. I thought it would be easier to kill myself. But my pride wouldn't let me do that. Then I knew the only thing I could do was prove my innocence."

Peter began to study law in prison and reopened his case in the high court in 1992. He was granted bail and the state decided not to order a retrial. Peter had proved his innocence. He was a free man. The other two men convicted of the killings are still in prison, 32 years later.

Life after prison was tough. Peter had no money and couldn't get a job. To this day, he has not been offered compensation by the state for the wrongful conviction and cannot find a senior counsel who will fight for recompense for him.

Relationships were difficult. It took time to rebuild a connection with his four adult children. "There had been a lot of pain. The whole family had been affected."

His first wife had long moved on and his partner at the time of his arrest, who helped him with his case while he was in prison and with whom he initially moved in, asked him to leave.

"It took a long time to feel comfortable around people. They look at you differently when you come out of prison. They'd ask what it was like, but I didn't want to talk about it. There's no way they could understand. Plus, the world had changed in 15 years. In Ireland, there was a new currency I had to learn to use. I'd never been in a supermarket before and I was amazed by the idea of a cashpoint. There were so many weird things I had to get used to."

Although Peter didn't like talking about prison, Sunny persuaded him to tell his story too, so that people could learn from it. He has just written a book, About Time, which details his prison experience, and now speaks frequently at human rights events with Sunny, despite his dislike of the limelight.

The couple have dedicated part of their lives to campaigning for human rights. When we meet, they are preparing to talk for Amicus, the legal charity that provides representation for those facing the death penalty in the US. The couple also support groups for disadvantaged people all over the world.

And they are setting up a charity for former prisoners who have been exonerated, and their families, to help them through the trauma of wrongful convictions. They plan to invite people to stay with them to allow them time to adjust to life on the outside, and give families a chance to heal. The project is called the Sunny Sanctuary.

But being exonerated doesn't define who Sunny and Peter are all the time. They have another life too now. Far from confined cells, they have made a deliberate choice to live a quiet, rural life in a cottage on three and a half acres of land, close to the sea in west Ireland. They keep chickens and goats. Peter beams when he mentions his seven grandchildren. Sunny teaches yoga classes locally. The couple meditate every day.

"At home, we don't talk about what it was like in prison. That's understood," says Peter. "We've been there, done that. That's the way it is."

Sunny adds: "We don't talk about who we were. We don't need to."

Despite the years they lost in prison and everything they have been through, they are not bitter. "Life has turned out beautifully," says Peter. "Sure, it's not without its difficulties. We have no money. But we do good work. We are at peace. And we have a great life together. We look forward, and we live in the moment."

About Time by Peter Pringle, published by The History Press Ireland, is out now, £14.99. To order a copy for £11.99, including free UK p&p, go to guardian.co.uk/bookshop or call 0330 333 6846