PARIS (AFP) - Two boys, two centuries apart. One died in agony in prison at the height of the French Revolution. Was he Louis XVII, France's uncrowned king, or - as legend would have it - was he a substitute, taking the place of the 10-year-old monarch who then fled to safety?
The other: Gregory Villemin, a four-year-old boy whose trussed body was found dumped in a remote river in eastern France. For 16 years, Gregory's killer has evaded detection. But a dab of saliva on a scrap of postage stamp, attached to a poison-pen letter, may now reveal all.
The sleuth called in last week to resolve these two mysteries goes under the name of molecular biology. Minute samples of DNA - as little as a thousandth the size of a grain of salt - are amplified by chemicals to reveal an individual's genetic identity. The data is transcribed into the form of a bar code that can be read by computer and compared with other samples with greater speed and precision than any fingerprint expert.
Skin cells or body tissue, blood, saliva or even nasal mucus can be used, as well as bone or hair from an ancient skeleton and, depending on the quality of the material, the results can be known in as little as six hours. "DNA fingerprinting has revolutionized not just forensic science but all sorts of other fields as well," says Matt Ridley, author of an acclaimed book, "Genome: The Autobiography of a Species in 23 Chapters."
The technique was introduced in a famous case in 1986, when British experts helped police solve a rape murder through testing semen samples, identifying the killer with more than 99.9% accuracy.
Since then, DNA has confirmed the identity of the exhumed corpse of Nazi war criminal Josef Mengele in 1990. It has found that Thomas Jefferson had illegitimate descendants from an affair with a slave. And it established the presidential origins of the semen on Monica Lewinsky's dress.
It has confirmed the identity of the remains of the Romanov family slain by Russian revolutionaries, and proved that a woman who passed herself off as Anastasia, supposedly a survivor of the massacre, was an imposter.
One of the new police station's major advantages is its low cost, with an initial investment of 250,000 kronor ($30,320) and an additional 40,000 kronor per year in overhead expenses.
DNA tests have found that a teacher in southwestern England is a descendant of a caveman who lived 9,000 years ago. And last month, DNA confirmed that the Neanderthals, who lived 28,000 years ago, were a hominid species in their own right and not our ancestors.
The technique has now entered the commercial field, with companies selling paternity tests to suspicious fathers and angry single mothers demanding child support, while other firms offer to DNA-tag oil consignments or food products to prevent illegal sale or forgery.
By far, the biggest use of the new technology has been the fight against crime. Hundreds of murderers and rapists have been convicted through DNA testing, and some people falsely accused of crimes have been proven innocent, sometimes decades after the event.
"It's one of the most cutting-edge techniques, ground-breaking, the most exciting investigative tool since fingerprinting was introduced," says Australian superintendent John Gillett, who launched a mass DNA screening in a small New South Wales town after a 91-year-old woman was raped. A 44-year-old man, who has now been charged with the crime, surrendered to police after all but 12 of the 600 men who fitted the age profile of the rapist submitted to the test.
More and more police forces are setting up DNA databanks. France announced plans in February. China said in March that it would set one up in an attempt to stop an alarming rise in child trafficking, storing the DNA fingerprints from the parents of the thousands of children who are kidnapped yearly.
Britain has the world's biggest database, with the genetic fingerprints of 600,000 offenders, and has unveiled plans that would enable police forces to take samples from anyone arrested for offenses that carry a prison term.
Civil-rights watchdogs fear DNA tests are being embraced without discrimination, with the risk of error or abuse. However sophisticated the technique, the results are never 100% certain, notes Ian Shaw, a professor of forensic science at Britain's University of Central Lancashire. And mass DNA screenings have an Orwellian tinge, for people who refuse to take part in the test will be perceived by the authorities or fellow citizens as guilty, say critics.
In New South Wales, Law Society human rights committee chairman Michael Antrum last week said the screenings in the town of Wee Waa yielded "a frightening glimpse of a future police state."
