Special Reports

SIR WILLIAM Tite paid to have his family's remains laid to rest in great splendour. As designer of the underground catacombs at West Norwood Cemetery in London in 1837, he gave pride of place to the Tite family tomb.

The platform on which his coffin lay would have been silently lowered from the chapel above by the hydraulic lift, or catafalque, and eased off by the waiting pallbearers straight into its resting place in the central aisle.

But the iron grille at the front of the Tite vault no longer reveals coffins draped in expensive velvet or embellished with polished metal plaques. Water drips down the brickwork of the dark, neglected vaults and the wooden coffins stacked in the recesses have warped and split to reveal the lead casing beneath.

Despite all his efforts to maintain his social status in death, Sir William Tite and his catacombs have gone the way of all flesh. Some still dream of preserving their mortal remains for eternity - perhaps even coming back to life - but we are scarcely closer to that dream since Sir William passed away. All that modern science can add is the ability to learn a great deal about a person's life and death from his corpse.

Unless frozen or mummified, dead bodies inevitably decompose. There are generally thought to be five recognisable stages of decomposition in death: fresh, bloat, active decay, advanced decay, and dry or skeletal remains.

As soon as the human heart stops beating, gravity takes hold. Sometimes only minutes after death, a purple-red stain appears where the blood settles in the lowermost parts of the body. The skin and muscles sag, the body cools, and within two to six hours rigor mortis sets in. Starting with a stiffening of the muscles in the eyelids, it spreads throughout the body before the muscles relax again. Rigor mortis can last between one and four days depending on various factors, not least the ambient temperature.

Two or three days after death, the body starts to putrefy. Bacteria which normally inhabit the body, and especially the bowel, take over. The first sign of putrefaction is a green discolouration which appears on the right lower abdomen above the caecum - that part of the bowel which lies nearest to the surface. It spreads over the entire abdomen, chest and upper thighs before darkening to purple and finally black. Bacteria in the intestine produce a rank smelling gas which bloats the body and makes the eyes bulge.

A week after death, blood-coloured blisters appear on the skin and the slightest pressure causes the top layer to slip off. After three to four weeks, the hair, nails and teeth loosen, and the internal organs disintegrate before turning to liquid. Finally nothing is left but the skeleton.

In his book, Vampires, Burial and Death, Paul Barber, a research associate at the Fowler Museum of Cultural History at the University of California, Los Angeles, describes how European folk tales of vampires often sprang from hysterical peasants who had witnessed normal postmortem changes in exhumed bodies. Instead corpses wasted by death - they found plump bodies, stained red faces and an unbearable stench. The bloody fluid seeping from the mouth, forced out from the ruptured lungs by gas pressure, was taken as a sure sign that the undead had been feeding on the living.

Many factors determine the rate of decay. But according to Kenneth Iserson, Director of the Arizona Bioethics Program at the University of Arizona Health Sciences Center and author of Death to Dust: What Happens to Dead Bodies?, it takes on average 10 to 12 years for an unembalmed adult body, buried 2 metres deep in ordinary soil, without a coffin, to decay down to its skeleton. A child's body takes about half that time.

Warmth accelerates decomposition and cold slows it down. Hence the almost complete preservation - tattoos and all - of ötzi the "Iceman", who was trapped 5000 years ago in a glacier in the ötztaler Alps on the Austrian border with Italy.

Bodies buried deep can outlast those in shallow graves. An increase in depth of less than a metre makes a body less accessible to worms and maggots. So a corpse buried 0.5 metres down may be reduced to a skeleton in a few months to a year, whereas the same process can take many years in one buried 1.2 metres down. A body which is wrapped in a polythene sheet will last longer for the same reason, but a body which is clothed and exposed may decay faster because maggots like the shade which clothing provides.

Soil chemistry and humidity affect decomposition, as does coffin material. According to Iserson, more than 150 preserved bodies, some 5000 years old, have been discovered in Danish peat bogs in the last two centuries. Their preservation is probably due to a combination of acid bog water and an almost complete absence of air.

The sites of London's plague pits, described in 1896 by the intrepid Mrs Basil Holmes in her book The London Burial Grounds, provide examples of the acceleration of decay. Mrs Holmes wrote that, "where the soil was saturated with quicklime, the coffins smashed at once, and decay in every way hurried", the remains were likely to be less grizzly than when corpses had been buried in coffins of lead or oak, "which only occasionally give way and let out the putrifactive emanations".

When the plague swept Britain in both 1348 and 1665, existing burial grounds and churches were overwhelmed. Emergency cemeteries had to be dug and many of the bodies were buried without coffins. One of the biggest pits dug for victims of the 1665 plague in London was in Aldgate churchyard. It was about 14 metres long, 5 metres wide and 7 metres deep and, according to Mrs Holmes, it received 1114 bodies in just two weeks in September 1665. Excavation of London's Royal Mint site in 1986 revealed the remains of victims of the 1348 plague buried up to five deep - in trenches no more than 2 metres deep.

Dying agents can preserve bodies. Roman cemeteries in Britain and North Africa have occasionally revealed evidence of "plaster burials", where lime, chalk or gypsum was packed around a body in a coffin. The undertakers of the time would have known of the drying properties of lime, and perhaps even of the antiseptic nature of gypsum, says Christopher Sparey-Green, a freelance archaeologist who studied plaster burials at a Roman hill fort on the outskirts of Dorchester in Dorset. He found that the hair of some of the corpses had been so well preserved that it was possible to study their hair styles.

When excavation began in the crypt of Christ Church, Spitalfields in London in 1984, it revealed 1000 bodies that had been buried there between 1729 and 1852. The discovery of adipocere, a waxy substance which results from the breakdown of fatty soft tissue, told the archaeologists what sort of conditions those individuals had been buried in. Natural mummification takes place in very dry or draughty conditions, putrefaction is rapid when a corpse is exposed to warm, damp air, but adipocere forms in conditions somewhere between the two. According to David Whittaker, a forensic dentist on the Spitalfields project, adipocere is most commonly found in lead coffins in dry vaults.

"The Christ Church excavation is unique in my experience because of the combination of historical data and scientific experiments," says Whittaker. "We were able to check our standard ageing techniques against the records of ages at death, and they turned out to be pretty accurate - within about six to seven years either way." Those techniques, based on analysis of teeth, have since been used to age the corpses unearthed in the Cromwell Street murder investigation.

The work at Christ Church was held up for almost two months in 1985 when smallpox pustules were found on one of the bodies. The Health and Safety Executive carried out tests on a sample which they declared to be unviable, but the question of whether there is a risk of catching diseases from exhumed bodies has not been fully resolved. Taryn Nixon, Head of Operations at the Museum of London Archaeology Service, says that protective clothing and vaccination against smallpox are routine precautions for archaeologists working on burial sites.

If a corpse is exposed to the elements, maggots play a large part in putrefaction. In fact, forensic entomologists can now determine the time of death and even identify murderers on the basis of insect evidence. According to the Wall Street Journal in April 1992, police in Tacoma, Washington traced the killer of a man who had been shot after entomological investigators found two generations of maggots in the body. One generation of maggots takes about three weeks to develop into adults, so the investigators could determine that the man had died just over three weeks before his body was found. Using that evidence, police calculated that he had died on the day of a party at a nearby house. It turned out that he had been killed by an accidental gunshot at the party.

The heat produced by a combination of insects and the bacteria which cause putrefaction can also help in the location of buried or hidden bodies. A report in the Journal of the Forensic Science Society in 1977, for example, described the use of infrared thermal scanning in a police search for a missing body in New Zealand.

In some parts of rural Greece, it is the custom to dig up the bones of dead relatives several years after burial. If flesh remains on the bones, they are reburied until a later date. But if all the flesh has gone, the bones are transferred to an ossuary and the grave reused. Reuse of burial grounds was also common in Britain until the 1830s, says Ian Hussein of the Institute of Burial and Cremation Administration in London. By that time, London's churchyards were almost full and the interval between successive burials was becoming so short that a body would not have fully decomposed by the time the grave was reopened to receive another corpse.

So large municipal cemeteries were created in the city. And at about the same time, burial in crypts and catacombs came into fashion for the well-heeled. Although only briefly popular in Britain, catacombs did have advantages. Apart from being able to display the social standing of your family by the grandeur of your private vault, there was less danger of being buried alive. The doors could be also be locked against opportunists.

But the Victorians underestimated the bodysnatchers. When a double wooden coffin was excavated from Christ Church, both bodies had been removed and replaced by rubble. And several dentures made from human teeth were extracted from the crypt. At that time, says Ruth Richardson, a research fellow in the history of medicine at University College London, it was common for dentures to be made from teeth removed from human cadavers by bodysnatchers.

While medical research relied so heavily on the illegal supply of corpses, bodysnatching remained a lucrative business. Beginning in 1540, English anatomists were legally supplied with a few criminals' corpses each year. Only in 1832, when the Anatomy Act was passed in Britain, did it become legal to use "noncriminal, technically unclaimed" cadavers for dissection, says Richardson. So the poorhouses then became a plentiful source of corpses and bodysnatching is reputed to have stopped. But in some states of the US, it continued well into the 20th century.

British undertakers made coffins which were designed to ensure "Safety for the Dead", but they were not always scrupulous when given a large fee to provide surgeons with fresh corpses. So William Horne, an undertaker buried at Christ Church, was probably more aware than most of the precautions needed to prevent his own resurrection. His coffin consisted of three shells, the middle one being lead. Iron rods strengthened the wooden lid of the inner layer and iron straps circled the outer wooden casing before being nailed into it.

Fear of being buried alive was a major Victorian preoccupation. Having witnessed the revival of a young girl from her trance-like state during the course of her funeral, Count Karnicé-Karnicki, Chamberlain to the Tsar, patented his "life-signalling" coffin in 1897. Any movement in the corpse's chest would trigger a spring-loaded ball, and a box on the surface connected to the spring by a tube would then open, letting light and air into the coffin. The spring was also designed to release a flag on the surface, a bell which rang for half an hour, and a lamp which burnt after sunset. But it is not clear whether any such coffin was ever built.

The interval between death and burial in Britain also lengthened. A comparison of death certificates and entries in the burial register for individuals buried at Christ Church revealed an overall increase from five days in the late 18th century to eight days in the early 19th century. By leaving the body until decay had set in, relatives might have felt reassured not only that the person was truly dead, but also that the corpse would lose its appeal for the bodysnatchers.

In ancient Egypt, the dead had to wait much longer to be buried. Accounts of royal burials describe how the embalming ritual involved a period of desiccation lasting forty days. And only after the drying-out period was the body washed, wrapped from head to foot in bandages and placed upright in a wooden casket.

Beauty in death was very important to the ancient Egyptians. During mummification they would pad the cheeks with sawdust and slide linen pads under the eyelids. Stones and small onions were even substituted for eyes. And their passion for embalming even stretched to their animals. The underground labyrinths of Tuna-el-Gebel in Egypt, for example, are packed with mummified baboons and ibises. A conservative estimate of the ibis mummies alone puts them at four million.

Embalmers at Moscow's Centre for Biological Structures managed to preserve Lenin's corpse (or possibly a wax-enhanced double) without bandages for 70 years. And they did the same for Joseph Stalin, Ho Chi Minh and Kim Il Sung. But there are cases of bodies which have remained mysteriously preserved without embalming.

The Naked Knight of Brandenburg, for example, lies in an open coffin in a dark room attached to the village church at Kampehl, wearing only a loincloth. He was born in 1651, he still has teeth, some hair and a penis, and his hands are clasped in a praying position. The story goes that he was a wealthy knight who was obsessed with women. When one young girl refused his advances, he beat her fiancé to death. Evading justice, he swore that if he was guilty, "then shall the good Lord never let my body rot". His curse, it seems, was at least as powerful as modern science.