WHEN she dies, Sunny Jacobs wants someone to plant tomatoes on her grave, or apple trees, or even a patch of curly kale and potatoes, just like the one in her back garden, so that she can still be a part of things. "But while I'm still alive I'm planting my seeds everywhere I go," vows the tiny, bespectacled American, whose joyful smile plays across her gamine features. And that, she says, is her revenge. "That is my legacy, and my memorial."

Jacobs, a 57-year-old grandmother, is a dead woman walking - although, in her case, walking free, after being sentenced to death for a murder she did not commit. She was locked up for almost 17 years - the only woman at that time in America who had a death sentence. She spent five years on death row, albeit one specially created for her by the Florida prison authorities, which cleared out an entire wing of an old prison for women, before locking her up in solitary confinement.

In 1976 Jacobs and her common-law husband, Jesse Tafero, were convicted of the fatal shooting of two Florida police officers, based on the false testimony of the man who had actually committed the murders. Like scores of other innocent men and women wrongly convicted and sentenced to death in the United States, Jacobs was eventually released in 1992, when the real killer finally confessed.

It was too late for Tafero, though. He had been executed two years earlier, in the most grisly botched procedure in the history of the American death penalty - the electric chair malfunctioned and the executioner had to pull the switch three times, sending three massive bolts of electricity through his body. Before it was over, Tafero's head burst into flames. "It took Jesse 131/2 minutes to die," says Jacobs wearily.

After they sentence you to death, they tell you exactly how they're going to do it, she continues calmly. "They say they are going to send 2,200 volts of electricity through your body until you are dead - then they ask if you have anything to say!"

The profoundly shocking story of the mother-of-two, who suffered an isolation from society that is beyond recompense, is just one of six death-row tales that are told in the award-winning play The Exonerated. A scorching indictment of capital punishment, it has been a phenomenal success in America, changing hearts and minds on the issue. It opens in Edinburgh on Tuesday.

All the stories related in The Exonerated, which was created by two young New York actors, Jessica Blank and Erik Jensen, authors of Living Justice, about the making of the play, are tragic and terrible. Each one is powerfully told in the words of the condemned people - but it's Jacobs' story that breaks your heart. Yet her heart is not broken, nor is her indomitable spirit. Sunny by name (her given name is Sonia) and sunny by nature, she says that laughter and living well are the best revenge for what has happened to her. "I honestly never think about revenge," she says softly, while trying to find a comfortable place to sit to ease the pain she suffers after being seriously injured five years ago in a car crash.

"Life sends all of us many trials - it's just that mine seem to be a little more dramatic than most," she tells me as she limps up to greet me warmly at the airport on the west coast of Ireland, where she now lives.

As a yoga teacher who does workshops for long-term prisoners, she can deal with pain, she says. She is just a little seized up after the long drive here. "I'll be fine tomorrow," she says with a wide smile. And you know that she will, because this is a woman of iron will and immense inner strength. "I'm a survivor," she says, banging her fist on the kitchen table. "I'm strong." And, she adds proudly, she ought to be in The Guinness Book of Records, since she has been portrayed by more actresses than any other woman alive.

In The Exonerated, Jacobs has been played by Susan Sarandon (who also starred as her in the TV movie version), Mia Farrow, Lynn Redgrave, Jill Clayburgh and many others. "With the exception of Mia, a lotta tall women have been me - and I'm so short," exclaims Jacobs, who has also played herself on stage and will do so for a limited run in Edinburgh, where the cast also includes Aidan Quinn and Robert Carradine.

Jacobs' heart-rending story never fails to move audiences to tears. "The play has given us a voice, but more importantly it has given Jesse a voice. As he was executed, he said, 'They're gonna remember my name.' And, thanks to The Exonerated, they do," she says.

Today, with the shimmering Atlantic Ocean virtually on her doorstep, and rolling green fields surrounding the rented farmhouse she shares with Peter Pringle, her 66-year-old partner - himself an exonerated death-row inmate, from Ireland - Jacobs has finally found freedom. Although, even when she was imprisoned in a tiny cell - "six paces from the door to the open toilet in the corner, and this wide," she says, stretching out her arms to demonstrate how she could touch the walls - she remained a free spirit.

"If you sit there rubbing two sticks together and crying on your sticks, they're never going to make a spark," she says. "But, you know, if you stop feeling sorry for yourself, just because you are determined not to believe in hopelessness, then a spark happens, and then you keep fanning that wee spark until you've got a flame. I realised that it was like a big trick." Then she quotes her own words in The Exonerated, "I was like Dumbo, and I put this feather in my nose and I flew, because I could fly anyway."

FORTY years ago, New York-born Sunny Jacobs, barely 18, fell pregnant and married her high-school sweetheart in Long Island, where she and her younger brother were raised by loving parents. "My childhood was very safe, very ordinary," she says.

The marriage broke down, leaving Jacobs a single parent, but blessed with a son, Eric. Then, when she was 23 - "a hippie mom and a vegetarian, believing only in peace and love" - she met Jesse Tafero, who had a police record that dated from his teenage years. But those misdemeanours would come back to haunt them. "I grew up with the romantic American dream, and I wanted that," recalls Jacobs. "All I dreamed of was having a loving husband and a father for my son; I was in love with Jesse, and I thought we would live happily ever after."

They were together for three years, and although they weren't officially married, she considered him to be her husband. She was the breadwinner, doing part-time jobs in North Carolina. In 1976 she had recently given birth to their daughter, Tina, when Tafero announced that he was going to get himself regular work - not easy, given his police record. But he just needed to go to Florida one last time to do a little deal. She didn't want to know the details.

Then he called, told her the deal had fallen through, that he was broke and had no way of getting home - "and he was staying with some girl". She said she would be right there to get him. "How stupid was that?" she wonders now. "But I loved him."

So she put nine-year-old Eric and ten-month-old Tina into her rusting car and set off. By the time she got to Florida, the car had broken down and couldn't make the long journey back. Tafero's friend, Walter Rhodes, offered them a lift part of the way home. Jacobs didn't like him, but he was willing to drive them north. "We had no money, nothing. And it was only a ride," she says.

Shortly after they set off, Rhodes pulled into a rest area to sleep. Early the next morning, two policemen, on a routine check, looked in the car, saw the sleeping passengers, then spotted a gun on the floor between Rhodes' feet. They called in to headquarters and discovered that he was on parole, and possession of a gun is a parole violation. At gunpoint, they ordered him and Tafero out of the car. Then the shots began.

Shielding her children in the car, the terrified Jacobs didn't know who had been hit. When it went quiet, she looked up and saw the two policemen were dead. Rhodes then kidnapped the family at gunpoint, taking them on a wild journey.

As they sped along the motorway, Jacobs heard helicopters and breathed a sigh of relief - they were about to be saved. Rhodes swerved to avoid a roadblock and the police opened fire on the car. Rhodes was shot in the leg; Jacobs and her family were uninjured. The cops dragged everyone out and brought them all in as suspects. Although she was scared, Jacobs was certain they would let her and Tafero go.

Paraffin tests on their hands established that Rhodes was the only one of the three who had fired a gun that day. But Rhodes was a career criminal and he knew the system. He immediately started arranging a plea bargain - one in which he would receive three life sentences and immunity from the death penalty, in exchange for serving as star witness against Jacobs and Tafero.

Tried separately, both Jacobs and Tafero were sentenced to death. She remained convinced that the police would find out she was innocent."I was so certain that I would be released that I kept my breast milk going for Tina for more than a year," she says. "I managed to get a plastic bowl and at midnight I would express my milk, so that I would still be able to nurse Tina when I got out. One day, though, I realised there was no point. She was no longer a baby."

She stayed sane by practising yoga, meditating, keeping a journal on toilet paper, and continuing her relationship with Tafero through love letters. They wrote to each other almost daily for 14 years - they each got Japanese dictionaries and used the language for their correspondence, because all mail was read by prison officers. "I existed on those letters," she remembers.

Meanwhile, Rhodes was also writing letters - to judges and prosecutors, in which he disavowed his previous testimony against the couple and took sole responsibility for the crime. Then he would recant his recantations, so that they both remained on death row. In 1982, though, the death sentence against Jacobs was overturned and commuted to life imprisonment. Rhodes was released on parole in 1994.

Fate was not done with Jacobs, however. Shortly afterwards, her parents were killed in a plane crash in Louisiana. "That was the most horrible day of my life," she recalls. "I saw it on the TV news; I knew that it was their flight."

But Jacobs was not without caring supporters. A childhood friend, Micki Dickoff, from Los Angeles, heard about her plight and was convinced of her innocence. She worked tirelessly for Jacobs and Tafero, bringing in a new defence lawyer and ultimately making a TV film about the case.

Despite these efforts, though, Tafero was executed. Then, two years later, Jacobs was freed, in large part based on the theory that Rhodes was actually the lone killer. It emerged that evidence in the couple's favour had been held back, including a polygraph test taken by Rhodes, which had been falsified.

After her release, Jacobs went to live in LA with Dickoff. "Everything had changed. I hadn't, though. Sure, I was 45, but it all moved too fast. I had to get used to crossing streets and opening doors. It was too much."

Taken up by the anti-death penalty movement, she became the face of their poster campaign - "This poor little woman, this pitiful victim. But I wasn't a victim! I was a survivor. Yes, I was wronged, but I was no victim. So I left the movement. I had to build some sort of life for myself and my children. We had to become a family again.

"We had a lot of difficulties. Tina and I made four attempts at living together; then my son came to live with us, with his three-year-old daughter, Claudia, now 16. We were an odd family, because we had been so damaged, robbed of all that time together, but somehow we survived. We connected."

After all those years on death row, what does the rest of your life look like? "It looks like this," replies Jacobs, contentedly surveying her cheerful kitchen, with pots of scarlet geraniums and family snapshots everywhere. "Peter and I have no money. We own nothing. We could walk away from here today with only two suitcases, and we would still be happy," she says.

Despite having received no compensation, Jacobs says, "This is the happiest time of my life; I've never known such peace, such love. It's a gift." At this she gazes up into Pringle's navy-blue eyes. And indeed, this gentle giant of a man, with his mane of snowy-white hair and beard, looks exactly like Santa Claus as he gift-wraps her in his muscular arms and kisses her pale cheek.

WHILE we talk, Pringle deftly prepares a hearty meal for us - picking fresh salad ingredients grown by Jacobs - and tells his own story. He was a fisherman who had recently separated from his wife (he has two sons, two daughters and five grandchildren) when, in 1980, he was arrested, tried, convicted and sentenced to death for the killing of a policeman and of committing armed robbery in Ballaghaderreen, County Roscommon. "When the crime was committed, I was at least 50 miles away, in Galway," he says.

"The police had pursued one of the perpetrators into the county, but they lost him. Then, for whatever reason, they decided to pick me up and fabricate evidence against me. I did not have a police record, although I had a political background and had been interned during the 1950s. Perhaps that was enough reason for them."

His death sentence (capital punishment was not abolished in Ireland until 1990) was revoked ten days before he was due to be executed. His sentence was reduced to 40 years' penal servitude, without remission. He spent almost 15 years in jail. Despite having left school at 13, he studied law and finally proved his innocence. In May 1995 his conviction was quashed. His fight for compensation is ongoing. "It's Dickensian. It's as if they're waiting for me to die," he says.

"The coincidences between our stories just blew me away," says Jacobs. They met when she was speaking at an Amnesty meeting in Ireland in 1998. "Then he tells me he survived by studying yoga and meditating. I realised I had finally met someone who knew where I had been, but also where I was going."

Jacobs' goals are now to build a good, meaningful life with her "big fella", help others to survive injustices and to understand the importance of healing and reconciliation, and to make just enough money from lecturing to visit her beloved grandchildren in the US.

But doesn't she feel any bitterness or anger over what happened to her? With some difficulty, she stands up, holds her iron-grey head up high, puts her hand on her heart and says, "They took away my name and I became a number. I was in there 17 years; I'm not gonna give them one more minute of my life."

• The Exonerated is at Assembly @ Queen's Hall, Edinburgh, from August 9 to 27. For tickets and information, call 0131 668 2019