It was the savage killing that gripped America - the six-year-old beauty queen found strangled in her parents' basement, a bizarre ransom note left on the stairs and an extraordinary cast of suspects. But 10 years after the death of JonBenet Ramsey, her killer remains at large. Gaby Wood travels to Colorado to meet the investigators still trying to solve one of the most notorious murders of the 20th century

The house on 15th Street isn't quite the house it used to be. Indeed, some effort has been made to claim that it no longer exists at all. Five years ago, the number was officially changed from 755 15th Street to 749. There is no 755 any more.

'The owners are anxious to sell it,' says the estate agent in charge of the empty mansion. 'It's been on the market for a while.' The house has five bedrooms and seven bathrooms. It's in a wealthy part of what is often referred to as a 'perfect town', just by the university campus and near the foot of the Rocky Mountains. The views are breathtaking. Nevertheless, I suggest, perhaps at $1.5m it's too expensive. 'Oh, it's worth the money by far,' says the estate agent. 'It's worth $2m. It's just that there's some history that has to be sorted out by whoever buys it ...' He tapers off, then adds: 'But I mean, it's been sold three times since the event.'

At 1.05pm on Boxing Day 1996, the body of six-year-old beauty queen JonBenet Ramsey was found by her father in the basement of this house in Boulder, Colorado. Her arms had been pulled up over her head and tied together at the wrists. A broken paintbrush had been used to tighten a garrotte around her neck. Her skull was severely fractured, but there was no blood. Her mouth was covered with duct tape. Her body showed signs of sexual abuse. She was blue, rigid, half-wrapped in a blanket, and stuck to the blanket was a pink Barbie doll nightie. John Ramsey pulled off the duct tape, untied some of the cord, picked up his daughter and ran, screaming, up the stairs. He put her down in the front hallway, at the base of the Christmas tree. His wife, Patsy, threw herself over the child's body and cried: 'Jesus, you raised Lazarus from the dead, please raise my baby!'

The police had arrived early that morning. They had been called at 5.52am, 20 minutes after Patsy had woken up and found a three-page handwritten ransom note at the foot of the stairs (the Ramseys were up early; they were due to leave for Michigan in their private plane at 7am). Strange as the ransom note was - long, literate, over-familiar, written with a pen and paper found in the kitchen and demanding a ransom that was the exact amount of John Ramsey's Christmas bonus - it was taken at face value. The case was treated as a kidnapping. Police searched the house and found nothing. At 10am, John went down to the basement: he found a window open and broken. Beneath it stood a suitcase on the floor. He closed the window and went back upstairs.

People were anxiously milling about, waiting for the kidnappers to call. Along with police officers, John and Patsy Ramsey had been joined by two sets of friends - the Whites and the Fernies - and Reverend Hoverstock, the Ramseys' pastor. Their nine-year-old son, Burke, was taken to a friend's house. Priscilla White started cleaning the kitchen, not thinking she might be destroying evidence. Just before one o'clock Detective Linda Arndt dispatched John Ramsey and his friend Fleet White to search the house again. And that was when, in the labyrinthine basement, behind a door that had been bolted shut, John found his daughter. White, who was a few feet behind him and claimed to have searched that room earlier, felt sure Ramsey had shouted, 'Oh my God!' before turning on the light.

Linda Arndt called headquarters and revised the initial report. It was not a kidnapping. It was a homicide. And the evidence had been smeared and left lying all over the place.

JonBenet Ramsey's was the only murder in Boulder that year. None of the Boulder police detectives who went on to investigate the case had ever dealt with a murder before, and this was the day after Christmas. The coroner didn't get there until after 8pm, and by the time he performed the autopsy the following morning, he was unable to determine the time of death. Within days, this was to become one of the most infamous murders of the 20th century. Pandemonium descended on the house, and on Boulder. One TV channel alone sent 20 people. Money started flying around - supermarket tabloids were offering to hire informants for vast sums and trying to buy copies of the ransom note for tens of thousands of dollars. A photo-lab technician stole autopsy photographs and sold them to The Globe newspaper. In 1996, 804 children were murdered in America. But the country didn't care about any of them as much as it cared about JonBenet.

A high metal fence now cuts across the front lawn of 749 15th Street, and fortifies the entire property. Recently planted trees shade the mock-tudor building from potential voyeurs. At the back of the house is a public alleyway that runs the length of the block. Local kids used to ride their bikes here, and if you look up you'll see a sign, a little obscured by overgrown branches: 'Children At Play'. Ten years ago, you used to be able to walk right into the Ramseys' back yard. Now, where the fence has been erected, a large, indelible letter has been carved deep into the bark of a big old tree. A capital letter for the capital crime that refuses to be forgotten: 'M'.

'I'll always rememberthat day. Shortly after dinner I got a call from my office saying that there was this kidnapping situation at a home in Boulder, nearby, and could I get over there.'

Charlie Brennan is a reporter for the Rocky Mountain News. He was the first journalist to arrive at the Ramsey home on 26 December, and he is perhaps the only one who has followed the story consistently for the past 10 years. In 1997, Brennan teamed up with Lawrence Schiller, who had written a bestseller about OJ Simpson, and conducted almost 600 interviews for a book that was to become the most authoritative on the Ramsey case, Perfect Murder, Perfect Town. Over breakfast in downtown Denver, he recalls those first days.

'Before I left home I called one source I had at the DA's office, and I was told that yes, it's a kidnapping, and the child is inside the home. And I thought, these facts do not belong in the same sentence. It sounded like the craziest kidnapping I'd ever heard of, and my source agreed, and said it did not add up.'

Statistically speaking, in cases where a child's body is found in the family home, the culprit is almost always a 'family member perpetrator'. Early on the morning of the 26th, when the Ramsey case was thought to be a kidnapping in a wealthy neighbourhood, the Ramseys were treated as victims. As soon as the body was found, they became prime suspects. Except that they were never exactly declared to be suspects - the foggy phrase 'under the umbrella of suspicion' was used. Police, however, appeared to have made up their minds. They thought, in the words of one ex-officer, that 'it was a slam-dunk case, and they would question people with the opening line: "The Ramseys say you did it". You don't say that to someone who could possibly be a suspect! When you focus on the Ramseys, you taint whatever you're going to get from other people.'

But the press went with them. It wasn't long before the police leaked the following: there were no footprints in the snow, and no signs of forced entry. The garrotte was an unusual method of strangulation, though one which was common in the Philippines, where John Ramsey had once been stationed at a naval base. The geography of the house was so complicated you'd have to be extremely familiar with it to know which was JonBenet's room and how to get to the basement. Both John and Patsy Ramsey told police that Burke was not awake when they called 911, but when the tape was analysed a third voice was heard in the background, and it sounded like Burke. Midway through the afternoon, John Ramsey insisted that he had to catch a plane. The ransom note, with its mysteriously precise sum and in-joke about John Ramsey's 'good southern common sense' (Ramsey was not from the south, Patsy was; that he had a more 'southern' character than she had was a family joke), was so long it was referred to by one FBI profiler as 'the War and Peace of ransom notes'. Clearly, whoever had written it on the Ramseys' notepaper had no fear of being caught in the act.

Charlie Brennan arrived to find a macabre scene. Patsy Ramsey's over-the-top Christmas decorations were still in place - red and white striped candy canes dotted along the walkway, white lights around the doorframe, an illuminated Santa in a sled on the snow-strewn front lawn. And all around the house, crime scene investigation tape, investigators' vans, police cars. There was only one other reporter there that night and Brennan thought: 'Where is everyone?' When the body was brought out, he remembers thinking, 'that's the most bizarre name. And I thought: this is going to be an unusual case.'

Eventually, other details emerged which competed with the original picture. Though there was no sign of forced entry, there was that small broken window into the basement that had been left open. Though there were no footprints in the snow, there was no snow on the part of the lawn that would need to be crossed to get in through the window. There was a footprint near the body left by a Hi-Tec boot. There was a latent handprint on the doorframe that didn't match any of the Ramseys'. If you looked closely, there were marks on the child's back and neck that were consistent with the use of a stun gun. The garrotte was viciously tightened: would a parent kill their child that way?

'When I had just come to Boulder,' says Brennan, 'my editors explained to me that it's an unusual community - it's described as 27 square miles surrounded by reality. They said, "We want you to look into the 'only in Boulder' story. The kind of story that couldn't happen anywhere else." Well, this is the "only in Boulder" murder. We're talking about a murder that occurred on Christmas night in which Santa Claus is actually a suspect. You can't make that up.'

For those committed to the intruder theory, there was no shortage of strange characters, though none was ever charged. Bill McReynolds had played Santa at the Ramseys' Christmas party three days earlier, for the third year in a row. He had been given a tour of the house, so he would have been familiar with its complicated geography, and he had written JonBenet a Christmas card saying that Santa would be giving her a 'special present' after Christmas. It was found in her rubbish bin after her death. On the very same day in 1974 - Boxing Day - McReynolds's nine-year-old daughter had been abducted with a friend, and had witnessed the sexual molestation of her friend. No suspects were ever found. In 1976, McReynolds's wife Janet had written a play in which a young girl is molested, tortured, murdered and left in a basement. Bill McReynolds died in 2002.

Other suspects cropped up: there was Gary Oliva, a convicted sex offender who had been seen hanging around the alleyway at the back of the house. He had spent time in prison for raping a seven-year-old girl in Oregon, and talked about making bacon out of a little girl's skin. In March 1997, a tip came in about Oliva: he had called a friend on 26 December and sobbed hysterically, saying he had done something terrible to a little girl. A year later, he attended JonBenet's memorial service. Four years later, two weeks before Christmas, he was arrested on the Colorado University campus for trespassing. The policeman who made the arrest searched his backpack and found a stun gun, a photo of JonBenet and an ode to her.

Chris Wolf, a freelance journalist, became a suspect when his girlfriend called the police and said he had stormed out of the house on Christmas night and come back the following morning, with muddy clothes. He became furious when he saw news reports of JonBenet's death on TV. The ransom note was signed 'S.B.T.C'; Wolf had a sweatshirt bearing those initials - they stood for Santa Barbara Tennis Club. He had written an article about John Ramsey's company, Access Graphics, and may have had access to information about his bonus. He was a friend of Bill McReynolds. The theory that there was more than one intruder has been seriously considered.

But the suspect who looked most likely was dead within two months of the murder. Michael Helgoth seemed to have shot himself the day after District Attorney Alex Hunter announced they were closing in on the killer. But this, too, began to look like murder. Helgoth was right-handed, but the trajectory of the fatal bullet went from left to right. In Helgoth's apartment were found a pair of Hi-Tec boots, a stun gun, a baseball cap with the letters 'SBTC' on it, and a videotape of a news story about the unsolved kidnap and murder of a six-year-old girl. If there were two assailants, could the other have silenced this one?

On New Year's Day 1997, Patsy Ramsey went on CNN. 'Hold your babies close,' she said. 'There's a killer out there.'

Ten years on, the case is still open.

Judith Phillips had known the Ramseys since before they moved to Boulder. They had lived in Atlanta together, Patsy had been a colleague of Judith's then-husband, the two women had been pregnant at the same time. Burke Ramsey and Lindsey Phillips were born a month apart.

Judith, a photographer, now lives in Denver with Tom 'Doc' Miller, a wild-eyed, electric-haired lawyer, private investigator and handwriting expert who she met through the Ramsey case. Miller is trying to find a publisher for his book about JonBenet's death. By way of introductory warning, he tells me that everyone who has written about JonBenet has profited from her death. 'Every drop of her blood has been sold! There's not enough blood in that girl's body to pay for all the ink that's been spent on her.'

Judith brings down a black and white photo she took of Patsy, Burke and JonBenet in the year before the murder. 'It haunts a lot of people,' she says. 'A lot of people have said they see a lot of evil in Patsy's eyes.' She pauses and fiddles with that opinion for a second. 'I'm too close to it, I don't know.'

In the photograph, Patsy is wearing a dramatically ruffled cream blouse; Burke is seated on her right; JonBenet is draped over her left shoulder, looking at the camera with hooded, seductive, melancholic eyes. It is the pose of a much older woman, a worn-out temptress, and she is heavily made-up with great sweeps of powder and shadow and dark, Fifties eyeliner. Later, when pictures of JonBenet as a miniature prom queen began to circulate in the supermarket tabloids, John Ramsey would say that they had been retouched. Yet here was the black and white truth of how Patsy wanted her children to be seen.

In the year of her death, JonBenet Ramsey had been crowned Little Miss Colorado. She had also been America's Royale Little Miss, National Tiny Miss Beauty, and Colorado State All-Star Kids Cover Girl, among others. In her youth, Patsy had been crowned Miss West Virginia, and so had her sister Pam. A special display case was made to house JonBenet's pageant trophies. Once, when Judith's daughter Lindsey Phillips asked JonBenet about these, she said: 'They're not really mine. They're more my mom's trophies.' JonBenet was dressed in outfits reminiscent of a Vegas showgirl; she wore tiaras and lipstick; her hair was lightened and curled; she was taught to dance provocatively. She was an icon of cross-dressing - crossing from girl to woman, from child to plaything. The month after her death, a photographer named Randy Simons, who had been hired by the Ramseys in June 1996 to take photographs of JonBenet in her pageant clothes, sold his JonBenet portfolio to Sygma Photo Agency for $7,500. A year later, he was arrested for walking naked in the street, crying, 'I didn't kill JonBenet!' He was hospitalised, and not considered a suspect.

Judith was out of town when the murder took place - which was just as well, she now says, 'because I would have been blamed. They blamed everybody. They blamed Fleet White - their best friend! When we came back to Boulder, nobody was talking to each other - everybody was afraid to discuss anything with anybody. I felt like I was in a Robert Ludlow novel.' Gradually, many of the Ramseys' friends fell away in the swell of suspicion. The Ramseys fought with the Whites at JonBenet's funeral; the Whites urged the governor to appoint an independent prosecutor.

'It's a sickening, sickening, sickening thing!' Doc Miller starts to shout. 'That little girl was murdered. And billions of dollars have been spent covering up her murder, unfortunately, by the press. You're as guilty as that woman if you print the goddam intruder theory. You're just taking more blood out of her. You'll come out of here with blood on your hands, Gaby!'

Judith gives me a copy of her latest coffee-table book, uncannily entitled Scream, Baby, Scream, and takes me into every room of the house but one. Glancing into this last, I see two rows of Sig-Sauer rifles, laid side by side on a double bed. There are so many guns that not an inch of bedspread is visible beneath.

One of the most immediately striking aspects of the Ramsey investigation was the dispute that broke out between the police department and the DA's office. The police detectives were led by Steve Thomas, who believed that Patsy had accidentally killed JonBenet in a bedwetting incident, and that the Ramseys had then staged it to look like a murder. The DA's office called out of retirement a legendary investigator from Colorado Springs, who had solved over 200 homicide cases: Lou Smit. Smit believed the Ramseys were innocent, that an intruder had entered the house and lain in wait in a nearby bedroom. He could be found, Smit thought, if DNA evidence was carefully considered. Foreign DNA was found under JonBenet's fingernails: 'I think she got a piece of her killer,' Smit said.

Two weeks after the murder, the results of a DNA test came back to the police. A drop of JonBenet's blood found in her underpants was mixed with the DNA of a Caucasian male, and no member of the Ramsey family was a match. It was six months before that report reached the DA's office. In August 1998, Steve Thomas resigned from the police department over the way the Ramsey case had been handled. In September 1998, Lou Smit resigned from the DA's office on the same grounds.

In 1999, just before the grand jury was about to be sworn in, the internationally recognised forensic expert Henry Lee was brought in. Yes, he suggested, the DNA in the underpants was not the Ramseys', but who was to say it was the murderer's? It could have been left there at any time, from the point of manufacture onwards.

'They were going to test all the Bloomingdales factory workers in Hong Kong, until they realised it wouldn't have made any difference,' says Bob Grant, former District Attorney for Adams County and adviser to the grand jury. 'I can make the whole argument - it came from the factory, it came from the cleaners, it came from the pants being placed in a hamper with other clothes that had other foreign DNA on them - it could have come from any number of places. But as a prosecutor, I've got to prove beyond a reasonable doubt. And foreign male DNA mixed with her blood in her underpants: that's reasonable doubt, by definition.'

The grand jury voted not to indict the Ramseys. At this point, for the prosecutors, the case was over - it was, as Grant realised early on, an 'unprosecutable case'. But the public battles continued. Steve Thomas wrote a book that laid the blame squarely on Patsy, and the Ramseys wrote a book listing other suspects. Both came out in 2000. The Ramseys sued Thomas, and settled. That year, Chris Wolf, one of the suspects listed in the Ramseys' book, sued them for defamation. But in order to prove his own innocence, he had to prove Patsy's guilt. In dismissing the case, federal judge Julie Carnes said that the evidence presented in that civil case suggested an intruder was more likely to have committed the crime than Patsy. In the Ramsey camp, it was widely thought this meant they had been cleared.

It has been pointed out even by those who once suspected them that in the past 10 years the Ramseys have not behaved as guilty people might. They wrote a book, which locked them into a version of the story; they sued Steve Thomas, which could have brought them into a courtroom; in 2004, John Ramsey ran for the state legislature in Michigan, where they now live - why would a guilty man do that knowing the scrutiny to which politicians are routinely subjected? And from time to time, when they pass through Boulder, the Ramseys meet with the DA to find out how the investigation is coming along. Those who have been in touch with them recently say the Ramseys are devastated and broke. 'They've been badgered and kicked and everything else,' said one acquaintance. They were contacted for this story, but remained silent.

I meet Michael Tracey in a place he refers to as his 'downtown office' - a bar called the Hungry Toad, which is owned by a Brit and is the only place in Boulder where you can buy a pint of bitter. Tracey is a professor of journalism at the University of Colorado; he has made three documentaries about the Ramsey case, is currently at work on a book about it, and has the ear of John and Patsy Ramsey, in whose innocence he firmly believes. He arrives with a manila envelope and tells me knowingly that he feels very close to solving the case. He can't say why, but he tells me that the DNA from JonBenet's underpants has now been tested accurately enough to be logged in the FBI system. Which means that anyone in any part of the country who has committed any crime for which a DNA sample is taken will automatically be cross-checked. Any day now, the FBI may find a match.

'This was not a staging,' Tracey says, pulling a photograph of JonBenet's neck out of his envelope. 'This was a vicious attack. There's no question in my mind now that someone came in who kind of knew them, who got off on little girls, extremely violent. She was asphyxiated - that begins to explain why there's no blood in the head - and he's getting off on this. I think they wanted to play with her. I think it was a very sick game by a very sick person.'

JonBenet's death gripped America, Tracey suggests, because it had everything going for it: 'Sex, sleaze, the rich father, the American dream gone bad... It was a combination of voyeurism, resentment, anger, irrationality, a cultural viciousness. It was Greek - a lot of people focused on it as a kind of catharsis.'

Where is the catharsis, I ask, if the case is unsolved? 'It's in the hate. Hate the Ramseys, you feel better. This was pretty close to a conspiracy.'

When Tracey pulled the image out of the manila envelope, I thought it was one I had already seen - a close-up of JonBenet's neck, designed to show the garrotte and the marks thought to have been made by a stun gun. But I noticed Tracey only pulled half the picture out of the envelope. The photographs I had seen were not close-ups but crops of this one. On instinct, I reached for the photo and pulled it out a little further. JonBenet's face came into view. She was lying down, and shot in profile. Her mouth was slightly open, her eyes were closed. If the photo had been in black and white, so that her skin's bluish tinge was invisible, you might have thought that she was merely asleep - until your eyes were drawn down to the fine blonde hair trapped under the cord with which she had been strangled. I looked at this photograph only briefly; in an unforeseeable split second I felt suddenly, swimmingly sick. Tracey's voice became background noise. Come on, I told myself, you're not squeamish. But back she came, the seemingly sleeping child. I started to sweat.

Later, I realised what it was about the photo that had haunted me: it was so ordinary. Over the course of many conversations, I'd become accustomed to hearing of 'the garrotted neck', 'the fingernails', 'the blood in the underpants'; these things were never hers. And the infamous pageant photos, haunting in their own perverse, made-up way, put her at several removes from herself. So in our minds she seems to have gone from icon to crime-lab fodder without passing through the most obvious and fundamental incarnation. I expected her body to look unrecognisable in some way, to be bloody or obscured or overly clinical. The last thing I expected it to be was what she was: a little girl.

The sign on Frank Coffman's door reads: 'The Crypt. Ring twice for best results.' Coffman makes horror masks for a living. He lives a few blocks away from the Ramseys' old house, and first became interested in the case because he lived nearby. Ten years ago, he was a regular Columbo, bumbling around, discovering where the cord and duct tape had been bought, befriending every nanny and cleaning person who had ever worked for the Ramseys. He has photographs and floor plans of the house. He has samples of Patsy's handwriting. 'A lot of people thought I had a kind of encyclopedic knowledge of the case,' he says, on the phone.

Later, as he leads me into his apartment, Coffman tells me he likes murder mysteries. 'I like books about the Lindbergh case, things like that. I know everything about the Kennedy assassination - that's pretty obvious really, when you look at the evidence. The Ramsey case has a lot of curlicues - it's still puzzling, even if you think you know who did it.'

As we wander down Boulder's central shopping street towards a coffee shop, Coffman tells me of a parade JonBenet took part in here just before the murder. She was dressed up 'as Little Miss Christmas, or something like that'. It was a tradition - the previous year she had sailed down the high street as Shirley Temple, singing 'The Good Ship Lollipop'. Then Coffman stops and tells me something that became lost as soon as the media frenzy began. 'She wasn't famous in Boulder, you know,' he says. 'I never heard of her before the murder. You get the impression that she was some kind of celebrity here. She was totally just another kid. Even though she was in that parade, nobody knew her. It's not like she was a target for a stranger. Her name never appeared in the newspaper before her murder. Her mother maybe wanted her to become famous, and maybe she was famous on the pageant circuit, but who the hell even was aware of that? Well,' he adds more slowly, 'she's famous now.'

I come back to my hotel and leave a message for Lou Smit. I've tried him through the DA's office for months without success, but now I have a number for his home in Colorado Springs and, although it's late, I can't get out of my mind the idea that so much of this hangs on him, whichever way you look at it.

If some of Smit's former colleagues are to be believed, he was swayed by his own religious convictions into believing the Ramseys were innocent. District Attorney Alex Hunter later said Smit got too close. Bob Grant, who had worked with Smit on a number of difficult homicide cases in Colorado Springs, says that in the Ramsey case 'people thought Lou was set up. The first time he met the Ramseys there was some kind of prayer group or something, and Lou's a very religious man. He got more so during his employment in Boulder. Patsy asked him to pray with them at the house - it felt natural to Lou. It should not have. I'm not saying it coloured his objectivity, but it certainly lends itself to that appearance.'

On the other hand, here was a man who had solved over 200 homicide cases, while the detectives in Boulder had not even investigated one. By the time he was called out of retirement to work on it, the evidence gathered was not as he would have wanted it. He told Michael Tracey, for instance, that had he been the first detective on the scene, he would have brought a dog in, which would have found the body in 30 seconds; he would have separated the Ramseys, asked them to come down to the station to give hair samples and blood samples; he would have taken their clothes and conducted initial interviews. Had they refused, he told Tracey, he would have arrested them. This from the man who believes most strongly in their innocence: an arrest would at least have given them the chance to clear their names.

There was another detail. In 1996, the year of JonBenet's death, Smit had solved one of Colorado's most puzzling crimes - the kidnap and murder of a 13-year-old girl called Heather Church. The trail had gone cold, Smit had been brought in and he'd solved the case on the basis of a latent fingerprint submitted to the FBI - years after the crime had taken place. Now he was suggesting that the Ramsey case could still be solved, 10 years on, using DNA evidence. Maybe he knew something others didn't.

Last year, Patsy's cancer recurred so aggressively that it was assumed she would die. Smit drove up to Michigan to visit her. Tracey speculates: 'I think he went to see her just in case.' In case of a confession? I asked. But why? He's on their side. 'No,' said Tracey, 'he's on the side of JonBenet. Now, does Lou Smit think the Ramseys killed JonBenet? No. But, would he just... a final... you know, just in case? Sure. That's how good he is.' In the letter of resignation he sent to Alex Hunter in September 1998, Smit wrote: 'Shoes, shoes, the victim's shoes, who will stand in the victim's shoes?'

The following morning, Lou Smit rings while I'm having breakfast. With direct, old-fashioned charm, he tells me he can't talk about the case because he is officially back inside it, and wants to remain that way in order to solve it. The DA, who has rehired him, has a strict policy of no publicity. But he does say he's hopeful, and tells me of others who are working on the case separately.

Ollie Gray and John San Augustin were hired by John and Patsy Ramsey in 1999. When the Ramseys ran out of money to pay them, the private eyes kept going. But it's hard. They needed the police to co-operate, and now that the police files have been handed over to the DA's office, they need the DA to co-operate.

'If they had put as much energy into investigating the crime itself as they did in trying to persecute the Ramseys, this thing would already have been put to bed,' says Ollie Gray. 'I'll bet you a nice steak dinner and a good bottle of wine that they have a bunch of evidence they have never processed. I think they have reports that basically prove that the Ramseys are innocent.'

On my last morning in Colorado, I go to meet Bill Wise, Alex Hunter's former deputy district attorney, at his home. His big white husky greets me at the door. Wise tells me that he was taken off the case for complaining about the police department's incompetence. I ask him why he thinks Smit has always believed in the Ramseys' innocence. 'I don't know,' he says, taking a deep drag on his cigarette. 'It would be because he is a much better investigator than me, and he sees things I don't see. He's a hell of an investigator. And if you can get a match anytime - murder has no statute of limitations... with all these databases that have been put together, there's a pretty good chance that DNA's gonna turn up sometime.'

In a corner of Wise's house is a framed Victorian picture. On the frame, it says it's a puzzle picture but, try as I might, I can't see the image two ways - all I can see is a pleasant pastoral scene. Eventually, I give up, and ask Wise to show me how it works. He laughs, and points a smoky finger at various details. 'There, see? That's a cat in the shrubbery,' he says, 'and there's a face there, and a crocodile down there.' Gradually, the whole hidden flip side comes into view - the English country scene is replaced by a fleeting kind of zoo.

'You can find them,' Wise says with a smile. 'You just have to look hard enough.'...