Candace Elizabeth Newmaker seemed like an average 10-year-old girl: all blue eyes, freckles and curly brown hair. Before she became a Newmaker she had been Candace Tiara Elmore, daughter of a teenage mother and violent father, and resident of a number of different ramshackle homes and trailers in a North Carolina backwater.

Her adoption at the age of five by Jeane Newmaker, a 42-year-old unmarried nurse, was supposed to change not only her name but her life. It was supposed to provide it with the certainty that a fragile mother and six different foster homes never could. At first it did: Candace got the pink bicycle, the riding, swimming and gym lessons, the ice-skating and slumber parties. But her adoption also led to her death.

Candace was suffocated in a bizarre, £5,000 process known as rebirthing. Wrapped in a blanket meant to represent a womb, the little girl was sat on by four adults until she could no longer breathe. She screamed for oxygen and told them she was dying, and the whole terrible procedure was watched by her new mommy.

On April 20, two unlicensed therapists, Connell Watkins and Julie Ponder, were found guilty of reckless child abuse resulting in death. On Monday, a judge sentenced them to 16 years in prison - the minimum sentence they could have received. Newmaker and two other assistants present during the little girl's ordeal are scheduled to go on trial later this year.

Her birth parents had called her Candace because they heard the name on television and Tiara because she was a "jewel". But Newmaker says that Candace was no gem, no average 10-year-old. She says the child had psychological problems so advanced that she started a fire in her own home, regularly flew into hour-long rages and once sexually assaulted two children. She confided in friends that Candace was a "handful" and "assaultive", and told a court: "I thought she was deteriorating before my very eyes. I was not prepared for the level of dysfunction I saw in Candace."

She says that Candace became "extremely defensive at home, extremely negative" and once pulled down a floor-to-ceiling bookcase, smashing Newmaker's beloved glass horses. Teachers remember a different child, one who was not badly behaved. But Newmaker felt Candace was so behaviourally disordered that she first put her on mood-altering drugs, then turned to a controversial therapy, believing Candace suffered from reactive attachment disorder, RAD, an increasingly popular diagnosis of extreme behaviour in children which is said to affect thousands of adoptive families.

The condition has divided the scientific and therapeutic communities, and has sparked the question: is this syndrome being used as an excuse for bad parenting or is it a little understood but growing phenomenon? Those who believe RAD exists - and many in the US do - claim that affected children cannot bond with their parents. That often they steal, lie, torture pets, hit their parents, hit themselves and lapse into extreme rages. With rebirthing, the idea is to turn back the clock and allow the child to bond. A kind of holding therapy, it involves a child lying across the laps of, or being contained by, parents or therapists or both. Often the child becomes angry and this is when the therapists tighten their grip. The aim is to show children that someone can control them and that they can feel safe at the same time.

Newmaker said: "I knew it was provocative therapy. I thought it was our only chance."

The unofficial home of attachment therapists is the mountainside town of Evergreen, Colorado. It was here that Candace was taken in April 2000 in a desperate attempt to control her behaviour: after a two-week course, she would be reborn. While there, she was subjected to a three-hour session of rebirthing during which she was told to "imagine yourself as a teeny baby inside your mother's womb and what it felt like". A videotape of the session shows Candace telling the adults in the room that she has a vague memory of being dropped from a window two flights up, that she had a nightmare last night in which she was murdered by her mother. She says she wants to feel safe.

The little girl was told she should scream and cry like a baby, and wriggle out of the blanket and away from the people lying on top of her. They said: "You're going to go through the birth canal" and promised: "While you are in the womb, you'll have plenty of air to breathe."

The four adults, weighing a total of 673 pounds against Candace's 70, began to apply pressure. In the video, Candace is heard to say: "Whoever is pushing on my head, it's not helping." Later she says: "I can't do it, I can't do it. I can't breathe, I can't breathe." A minute later, the child says she is going to die. She screams: "Please, please stop pushing. I can't breathe. OK, I'm dying, I'm sorry."

At this point, the therapists shout: "You want to die? OK, then die. Go ahead, die right now."

Twenty minutes later, still begging for help, Candace says: "Please, you said you would give me some oxygen" and: "I'm throwing up. I just threw up. I gotta poop. I gotta poop."

Still the adults keep going calling her a "quitter" and a "twerp", telling her that she gets to be stuck in her "own puke and poop". Finally they ask Candace if she wants to be reborn. "No," she says. It is the last word she ever utters. When the blanket is removed, Candace is blue. After a night on life support at a children's hospital, the little girl who had dreamed of being murdered dies from brainstem herniation and cerebral oedema, brought on by mechanical asphyxiation. Eleven times, she had told the adults that she was going to die.

In a statement in court, Connell Watkins said: "Candace's death is a tragedy and so is her life. I think of her story as being an American tragedy because there are thousands of children in this country today who have suffered trauma during their first two years of life ... they will also be misdiagnosed and mistreated, and ineffectively treated for years. Many of them, if they're lucky, will be adopted by loving parents, much like Jeane Newmaker. And they will devote all their resources and all their energies to help heal their children from the emotional and behavioural problems that they didn't create, and when and if they fail, they will be blamed."

Candace is the only child to have died during rebirthing but attachment disorder has featured as a defence in a number of recent trials. In 1997, Renee Polreis was sentenced to 22 years in prison for the death of her adopted son, David. She argued that he was not beaten to death with a wooden spoon but suffered from RAD which made him impossible to control and caused him to mutilate himself.

Joseph and Heather Ciambrone claimed that RAD led to the death in 1995 of their adopted son, Lucas, who was covered in more than 200 bruises when he was taken to hospital. They, too, said the wounds were self-inflicted. Joseph was sentenced to life imprisonment, Heather will go on trial later this summer and will plead insanity.

RAD first appeared as a recognised psychiatric disorder in 1980 and is defined by the American Psychiatric Association as "markedly disturbed and developmentally inappropriate social relatedness". While most researchers acknowledge that the syndrome exists, many argue that it is overdiagnosed and has led to the emergence of an entire industry of profit-motivated therapists with unproven treatments.

Thais Tepper, of the Parent Network for the Post-Institutionalised Child, believes RAD exists but says rebirthing is not the way to cope with it. "There is no basis in science for this treatment. How can screaming at a 10-year-old and torturing her until she accepts another woman as her mother really forge any kind of bond?"

Candace will now be remembered by Candace's Law, which outlaws rebirthing as a treatment in the state of Colorado.

Back in a trailer at the end of a muddy lane in Hickory, North Carolina, Candace's real mother, Angie, who has five other children, says: "They smothered her. That was my daughter. How did she die from a blanket? Isn't that why they say don't put pillows on babies, don't put bags by them? It's stupid, it's stupid. You don't put a child under a pillow and push on her."