In 1993, three eight-year-old boys – Steve Branch, Michael Moore and Christopher Byers – were murdered in West Memphis, Arkansas. "It was the subject of every newscast, on the front page of every newspaper, it was all they were talking about on the radio," Damien Echols says. "If you went to the grocery store, that's what they would be talking about in the checkout line." He remembers a sense of fear coming over the town. "You could feel it like a thunderstorm in the air."

Echols was 18 at the time, and his friend Jason Baldwin was two years younger. "There were three cops, a sort of juvenile task force, who used to harass pretty much every kid in our neighbourhood." One of them, Echols says, was convinced that Satanists were responsible for every bad thing that happened in town; he would show people Polaroid photos of roadkill – possums and raccoons run over by cars – and bizarrely claim it was evidence of animal sacrifices. "These cops had been harassing me and Jason for about two years before they finally decided they were going to pin these murders on me."

A month after the murders Echols, Baldwin and another youth, Jessie Misskelley, were arrested. Misskelley has an IQ of 68; after he had been interrogated for 12 hours, alone, he signed a confession that implicated both Echols and Baldwin. At their subsequent trial, evidence introduced by the prosecution included the fact that Echols wore Metallica T-shirts and read Stephen King novels. Echols had an alibi for the time of the murders – he was at home with his grandmother, mother and sister, not to mention that he had made phonecalls to three different people that evening. "That didn't matter to the jury," he says. "The local media had run so many stories about Satanic orgies and human sacrifices that by the time we walked into that courtroom the jury saw the trial as nothing more than a formality. It was over before we even walked in."

All three were convicted; Jason and Misskelley were sentenced to life imprisonment and Echols received three death sentences. "Even though I'd expected the verdict," says Echols, "part of me was still in denial. In the US, from the time you're old enough to speak you hear about how you're innocent until proven guilty and you have all of these rights. Part of me was still thinking that someone's going to put an end to this, someone's going to stop and do the right thing."

Marked by pain: Echols today. Photograph: Jared Leeds/AP

Over the 18 years that followed, Echols saw his mother a handful of times, his sister twice. His adopted father died while he was in prison. He also met the woman who was to become his wife – Lorri Davis, who wrote to him after seeing a documentary about the murders. Lorri took up his case, taking out personal loans to fund his defence. One day the film director Peter Jackson and Fran Walsh, his partner, sent Lorri a donation to the defence fund along with a note offering any help they could. "Peter and Fran would go to work in the daytime and make films like King Kong and The Lovely Bones," explains Echols, "and then they'd come home at night and work on this case. They had to give themselves a thorough education in the American judicial system. I would be dead right now without them."

New DNA evidence couldn't exonerate the West Memphis Three, as Echols, Baldwin and Misskelley had become known. But it did throw enough doubt on their convictions to force a deal from the state prosecutors, and in 2011 they were offered an "Alford plea", which allowed them to accept a plea bargain while maintaining their innocence (so the state would not be held accountable for any miscarriage of justice). They all were released immediately.

Damien Echols on the day of his arrest in 1993. Photograph: Richard Gardner/Corbis

"You don't get used to being in prison in a single day," says Echols, "and you don't get used to being out of prison in a single day. For several months I was in a state of profound shock and trauma. I'd been in solitary confinement for 10 years, so I wasn't even used to having human interaction. As time has gone by it's gotten better and better."

Last September he and Lorri moved from New York to Salem, Massachusetts, where the infamous witch trials took place. Echols had become a Buddhist in prison, and been ordained into the same Zen tradition used to train the Samurai. Last month he opened his own meditation centre.

Damien Echol's diary



Facing time: mug shots taken of Echols at the time of his arrest.

The night I arrived on Death Row I was placed in a cell between the two most hateful old bastards on the face of the earth. One was named Jonas, the other was Albert. Both were in their late 50s and had seen better days physically. Jonas had one leg, Albert had one eye. Both were morbidly obese and had voices that sounded like they had been eating out of an ashtray. These two men hated each other beyond words, each wishing death upon the other.

I hadn't been here very long when the guy who sweeps the floor stopped to hand me a note. He was looking at me in a very odd way, as if he were going to say something, but then changed his mind. I understood his behaviour once I opened the note and began reading. It was signed "Lisa", and it detailed all the ways in which "she" would make me a wonderful girlfriend, including "her" sexual repertoire. This puzzled me, as I was incarcerated in an all-male facility. There was a small line at the bottom of the page that read, "PS Please send me a cigarette." I tossed the note in front of Albert's cell and said, "Read this and tell me if you know who it is." After less than a minute I heard a vicious explosion of cursing and swearing before Albert announced, "This is from that old whore, Jonas. That punk will do anything for a cigarette." Thus Lisa turned out to be an obese 56-year-old man with one leg.

It proved true that Jonas would indeed do anything for cigarettes. He was absolutely broke, with no family or friends to send him money, so he had no choice but to perform tricks in order to feed his habits. He once drank a 16-ounce bottle of urine for a single, hand-rolled cigarette. I'd be hard-pressed to say who suffered more – Jonas, or the people who had to listen to him gagging and retching as it went down. I do not wish to leave you with the impression that Albert was a gem, either. He was constantly scheming and scamming. He once wrote a letter to a talk-show host, claiming that he would reveal where he had hidden other bodies if the host would pay him $1,000. Being that he had already been sentenced to death in both Arkansas and Mississippi, he had nothing to lose. When he was finally executed, he left me his false teeth as a memento. He left someone else his glass eye.

For all the insanity that takes place inside the prison, it's still nothing compared with the things you see and hear in the yard. In 2003, all Arkansas Death Row inmates were moved to a new "super maximum security" prison in Grady, Arkansas. There really is no yard here. You're taken, shackled of course, from your cell and walked through a narrow corridor. It leads to the "outside" where, without once actually setting foot outside the prison walls, you're locked inside a tiny, filthy concrete stall, much like a miniature grain silo.

There is one panel of mesh wire about 2ft from the top of one wall that lets in the daylight, and you can tell the outdoors is beyond, but you can't actually see any of it. There's no interaction with other prisoners, and you're afraid to breathe too deeply for fear of catching a disease of some sort. I went out there one morning, and in my stall alone there were three dead and decaying pigeons, and more faeces than you could shake a stick at. When you first enter you have to fight against your gag reflex. It's a filthy business, trying to get some exercise.

In the movies it's always the other prisoners you have to watch out for. In real life, it's the guards and the administration. They go out of their way to make your life harder and more stressful than it already is, as if being on Death Row were not enough. I didn't want these people to be able to change me, to touch me inside and turn me as rotten and stagnant as they were. I tried out just about every spiritual practice and meditative exercise that might help me to stay sane over the years.

I've lost count of how many executions have taken place during my time served. It's somewhere between 25 and 30, I believe. Some of those men I knew well and was close to. Others, I couldn't stand the sight of. Still, I wasn't happy to see any of them go the way they did.

I have the shape of a dead man on the wall of my cell. It was left behind by the last occupant. He stood against the wall and traced around himself with a pencil, then shaded it in. It looks like a very faint shadow, and it's barely noticeable until you see it. It took me nearly a week to notice it for the first time, but once you see it you can't unsee it. I find myself lying on my bunk and looking at it several times a day. It just seems to draw the eyes like a magnet. God only knows what possessed him to do such a thing, but I can't bring myself to wash it off. Since they executed him, it's the only trace of him left. He's been in his grave almost five years now, yet his shadow still lingers. He was no one and nothing. All that remains of him is a handful of old rape charges and a man-shaped pencil sketch. Perhaps it's just superstition, but I can't help but feel that erasing it would be like erasing the fact that he ever existed. That may not be such a bad thing, all things considered, but I won't be the one to do it.

At one point I entertained thoughts that perhaps the living inmates weren't the only ones trapped on Death Row. After all, if places really are haunted, then wouldn't Death Row be the perfect stomping ground? At some time or another it's crossed the mind of everyone here. Some make jokes about it, like whistling to yourself as you pass the cemetery. Others don't like to speak about it at all, and it can be a touchy subject. Who wants to think about the fact that you're sleeping on the mattress that three or four executed men also claimed as their resting place?

The silence on Death Row is something that seems to unnerve guards when they first get assigned here. That's because every other barracks sounds like a madhouse. There are people screaming at the top of their lungs 24 hours a day, it never stops. Screams of anger and rage, begging, threatening, cursing — it sounds like the din of some forgotten hell. These are the "regular" prisoners. As soon as you step through the door of Death Row it stops.

‘I was in solitary for 10 years, so I wasn’t used to human interaction’: Echols in prison. Photograph: Jeff Dailey/Sony

Sleep deprivation is a direct result of the lights. They turn them off every night at 10.30. Then they're turned right back on at 2.30, when they start to serve breakfast. If you could fall asleep the moment the lights went out, then sleep through all the guards' activity, you would still get only four hours of uninterrupted sleep. It's not possible, though. Doors slamming, keys hitting the floor, guards yelling at one another as if they're at a family reunion – it all wakes you up. You can never sleep very deeply here anyway, because you have to stay aware of your surroundings. Bad things can come to those caught off guard.

One of the first things I learned when I arrived was how to cook on a 100-watt lightbulb. This is accomplished in one of two ways. The first is by using the bulb directly, as a heat source. To use the bulb like an oven, you first cut the top off a soda can with a disposable razor blade. You then fill the can with whatever you want to cook – coffee, or leftover beef stew, for instance. You make certain the can is completely dry, not a single drop of water on it, and then balance it on the lightbulb. After 20 or 30 minutes, whatever is in the can will be hot enough to burn your mouth. You have to be certain the can is dry, because the bulb will explode in your face if water drips on it. You can always tell when someone has made this mistake – the explosion sounds like a shotgun blast.

For a split second today I could smell home. It smelled like sunset on a dirt road. I thought my heart was going to break. The world I left behind was so close I could almost touch it. Everything in me cried out for it. It's amazing how certain shades of agony have their own beauty. I can't ever seem to make myself believe that the home I once knew doesn't even exist any more. It's still too real inside my head. I wish I had a handful of dust from back then, so that I could keep it in a bottle and always have it near.

Time has changed for me. I don't recall exactly when it happened, and I don't even remember if it was sudden or gradual. Somehow the change just crept up on me like a wolf on tiptoe. Hell, I don't even remember when I first started to notice it. What I do remember is how when I was a kid every single day seemed to last for an eternity. I swear to God that I can remember a single summer day that lasted for several months.

Now I watch while years flip by like an exhalation, and sometimes I feel panic trying to claw its way up into my throat. Time itself has become a cruel race toward an off-coloured sunset. Forever can be measured with a ruler, and eternity is no longer than a stiff breeze.

God, I miss the sound of cicadas singing. I used to sit on my front porch and listen to those invisible hordes all screaming in the trees like green lunacy. The only place I hear them now is on television. I've seen live newscasts where I could hear them screeching in the background. When I realised what it was I was hearing I nearly fell to my knees, sobbing and screaming a denial to everything I've lost, everything that's been stolen from me. It's a powerful sound – the sound home would make if it weren't a silent eternity away from me.

Hearing the cicadas is like being stabbed through the heart with blades of ice. They remind me that life has continued for the world while I've been sealed away in a concrete vault. I've been awakened on many nights by the feel of rats crawling over my body, but I've never heard summer's green singing.

Star and stripes: Echols with Johnny Depp, a supporter of the West Memphis Three. Photograph: Rex Features

A single letter would have been enough to kindle a tiny spark of hope in my heart, but I received hundreds. Every day at least one or two would arrive, sometimes as many as 10 or 20. I would lie on my bunk and flip through the letters, savouring them like a fat kid with a fistful of candy, whispering, "Thank you… Thank you," over and over again. I clutched those letters to my chest and slept with them under my head. I had never been so thankful for anything in my entire life.

I had been on Death Row for about two years when I received an odd letter, in February 1996. It was from a woman who loved movies and had recently seen the documentary about my case at a film festival in New York. Her name was Lorri Davis, and she did something no one else had ever done – she apologised for invading my privacy by seeking me out. That really struck me, because I felt like I no longer had any privacy. My entire life had been exposed for anyone and everyone to examine and poke at with a stick. I was a fly that had its wings ripped off by a malicious kid. Every day I received letters from people who did nothing but ask questions about the most intimate aspects of my life.

Here was a lady who understood courtesy. She said she felt horrible about what I'd been through and was compelled to contact me, but she didn't want to intrude. I immediately wrote back to her, and ever since we have tried to write to each other every single day. Our letters to each other now fill up an entire closet.

She was from New York, college-educated, a world traveller who'd been to South America and as far away as the Middle East, and an architect who had worked on projects for people I'd heard of only from Hollywood movies.

We wrote to each other obsessively, and we spoke on the phone for the first time a month or so after that first letter. I just decided to call her one day – I was terribly nervous, knowing I'd need to improvise the conversation rather than script it ahead of time. She always laughs now when she tells anyone about the first time I called her. She picked up the phone to hear a deep, Delta accent ask, "Are you OK?" It was such a shock to her system that it took a second for her to reply. She said it nearly killed her.

Lorri came to visit me about six months later. I remember it was summer because she wasn't wearing a coat. It was a slow and gradual process, forging ahead together. I knew I was in love with Lorri when I started to wake up in the middle of the night furious and cursing her for making me feel the way she did. It was pain beyond belief. Nothing has ever hurt me that way. I tried to sleep as much as possible just to escape. I was grinding my teeth down to nubs. Now, years later, it's exactly the opposite. Now there is no pain, yet she still makes my heart explode.

For the first two years we knew each other, Lorri flew from New York to Arkansas about every other month, so, in addition to the phone bill, this was an extremely expensive relationship for her. When she came to see me, there was a sheet of glass separating us. It was maddening, and we would often blow through the screen at the bottom of the glass just to feel each other's breath.

Lorri and I weren't able to touch each other at all until December 1999, when we were married. After we were married, Lorri and I were permitted to be in the same room with each other, but every visit we had was chaperoned.

Lorri had moved to Little Rock in August 1997 to start a whole new life and to be near me. She kept and still keeps every aspect of my life – and my ongoing legal case – neatly filed and managed. During the first two years of my incarceration, not one single thing was done by anyone on my behalf. It was Lorri, and Lorri alone, who changed that. It didn't happen all at once. As Lorri became a part of my life, she began to educate herself, learning more and more about the legal process. When it became apparent that the public defender was going to get me killed, Lorri started doing research into defence attorneys. When she found someone she believed could do the job, she'd hound them until they agreed to take the case. When it was time to pay them, she begged and borrowed until it was done. She took loans from family members and friends, too.

She had to learn every single detail of the case, inside and out – names, dates, places, everything. She had to be my spokesperson, my representative. There is no one else in the world who could have done what she did, accomplished what she accomplished.

Life After Death by Damien Echols, is published by Atlantic Books on 1 June (£12.99). To order a copy for £10.39, with free UK p&p, click on the link or call 0330 333 6846