Lost dental records and DNA-laden toothbrushes, scattered relatives and bodies swiftly decomposing in warm, infested waters will make identifying the perished victims of Hurricane Katrina a daunting process, say forensic experts.
"There will be people that we will never be able to get a positive identification for," says Ray Wickenheiser, a forensic scientist at the Acadiana Crime Lab in New Iberia, Louisiana, who has helped draw up guidelines for the collection of forensic evidence in the wake of Katrina.
Until a few days ago, disaster response was focused on rescuing the living. But now the emphasis has shifted to recovering bodies before crucial evidence is lost. So far, 279 have been confirmed dead in Louisiana and 211 in Mississippi.
"The key is to get the bodies into refrigeration so they can halt the decomposition," says Lawrence Kobilinsky, a forensic scientist at the John Jay College of Criminal Justice in New York City, US, who says bacteria, rats and even alligators are now preying on the bodies.
The US Federal Emergency Management Agency's (FEMA) Disaster Mortuary Operational Response Team (DMORT) is retrieving bodies, along with any jewellery and documents found nearby, and putting them in refrigerated trucks.
At the mortuary or coroners office, DMORT takes digital dental X-rays, photographs, fingerprints and a DNA sample. Then a team matches them with pre-existing data - dental records, fingerprints on police files or found around the house - and DNA, either from items the individual owned, or from close blood relatives.
But the process is "tremendously difficult", say several forensic scientists. "The level of mass fatality, the mass disruption and displacement of people, the intense heat and lots of water. These are the things that caused the problems in Thailand following the tsunami," says Sue Black, a forensic anthropologist at the University of Dundee, UK, who identified bodies in Thailand. These factors "are all present in New Orleans".
But although lessons in body identification have been learned from the tsunami in 2004 and the collapse of the World Trade Center in 2001, Hurricane Katrina presents a unique set of problems.
The tsunami washed in and then washed out, while the water from the hurricane has stayed, allowing bodies to putrefy, says Wickenheiser. Warm water accelerates the rate that bacteria feed on soft tissue, causing skin to fall away in sheets, and releasing gases that bloat the body. Age and race become difficult to determine, faces are unrecognisable, tattoos are lost and it becomes impossible to take fingerprints.
In Asia, the vast majority of people were eventually identified by their dental records, which last longer than fingerprints or face recognition. But this may not be possible in New Orleans, where computers containing dental records have been swept away and the dentists themselves may have fled.
Wickenheiser believes that much of the identification process will come down to DNA, which is much more time-consuming and expensive than other methods, but which can be carried out from bone, long after bodies have decayed.
Nuclear DNA is ideal, and the best for identifying the individual from their brothers' or sisters' DNA. But toothbrushes or hairbrushes necessary for providing a home-specific DNA sample - which were available in the case of World Trade Center attacks, since those victims' homes were not involved in the tragedy - were in many cases swept away along with the hurricane. The next best thing is samples from next-of-kin relatives, such as parents, siblings and children, but they too may have been displaced.
Murder and rape
The other option is mitochondrial DNA, which is found in much larger amounts in cells and has a ring structure more resistant to decay. Extracted from bone, this was used in Bosnia to identify victims of war crimes. Because it is passed down from mother to child, even cousins could be used to identify one another, but it is also impossible to tell siblings apart from their mothers or children using this method.
Another confusing and unique factor could be that there will also be bodies recovered of people who did not drown but were killed in the crime wave that followed the hurricane.
"When the planes hit the twin towers, the probability that someone was being raped or murdered at the same time was very low," says Wickenheiser. "We are collecting not just information that leads to identity, but potential forensic evidence as well."
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