Identification of the dead relies on DNA samples from relatives

On Friday, there was a strange feeling of celebration at Ground Zero, as the rescue site has come to be known. It was not because anyone was found alive, but because six bodies had been found intact. Such have expectations lowered in New York.

On Friday, there was a strange feeling of celebration at Ground Zero, as the rescue site has come to be known. It was not because anyone was found alive, but because six bodies had been found intact. Such have expectations lowered in New York.

Usually, the 3,000 workers deployed at the smoking mass of concrete, glass and metal find only body parts. Last week, a watch was found that had stopped at 9.04am, the time disaster struck the World Trade Center. Distressed workers found it attached to a severed arm.

Once found, body parts are recorded and put in bags to be sent to the Medical Examiner's office in downtown New York, while identifiable bodies are sent to various mortuaries across the city. In the immediate aftermath of the carnage, the federal Department of Health and Human Services sent 169 mortuary specialists from around the country to New York. Massive extremes of heat, weight and trauma applied to bodies add to the difficulties of the identification procedures ahead.

"It will be a horrendous process," said Dr Robert Kirschner, a former Cook County deputy medical examiner who helped to identify 273 people who died in a plane crash at O'Hare International Airport in 1979.

Where possible, Dr Kirschner said dental records or fingerprints will be used for identification, but in cases where only parts of an individual are found, DNA will be used.

The key, he said is the part of the genetic code called mitochondrial DNA which is passed almost unchanged from mothers to their offspring. "All you need is a maternal relative – a sister, brother mother or maternal grandmother," he said. To facilitate identification, relatives of the missing have been queueing at a Red Cross family centre at Pier 94 in west Manhattan with dental and medical records and possessions from their loved ones that might contain remnants of DNA – a toothbrush, hair brush, razor, nail scissors.

Mothers, where possible, have been asked for swabs of saliva which will be stored on a database and cross-referenced with DNA extracted from body parts found in the debris. It is a heartbreaking process, and one that the authorities say could take several months to complete.

Professor Bernard Knight, a leading forensic scientist at the University of Wales in Cardiff, said yesterday that each unidentified body part will have to be X-rayed and meticulously catalogued. "A lot of it is organisational rather than medical. There's been nothing this big as far as I can remember," Professor Knight said.

The easiest way of identifying corpses will be visual identification using personal effects, wallets, jewellery and other property found on a body.

Martin Evison, senior lecturer in forensic and biological anthropology at Sheffield University, said that dental records and DNA profiles of tissue remains, compared against the DNA of relatives, will be the two main ways of identifying the most horribly mutilated corpses or body parts that have no identifying marks.

"Obviously you've got to draw the line somewhere. Not every piece of tissue is likely to be profiled, and where the bodies are badly burned and DNA destroyed, dental records will be used when possible," said Dr Evison, who took part in the task of identifying the bodies of genocide victims in Kosovo.

For partial skeletons, forensic pathologists will attempt to estimate the person's age, height and sex from thigh bones and pelvis.

The skull can give an overall idea of a person's geographical origins, essentially whether they are African, Indo-European or Oriental.

This will help pathologists to categorise bodies into broad groups of individuals to compare against reported missing persons. If a visual identification involving next-of-kin or dental checking is not possible, then DNA profiling will be used as the ultimate fallback.

However, there is a distinct possibility that the people who were nearest to the explosions and the subsequent fires may never be identified.

"Vaporisation may be too strong a word to use, but certainly for some people, their remains may have been reduced to ashes," said Dr Evison, whose department at Sheffield has offered to help the American authorities in their delicate task.