It began with a brutal double murder on July 5, 1692.  A wine merchant and his wife were killed in the cellar of their shop in Lyons, France. Since the money known to be in the shop was missing, authorities concluded that the couple had been robbed and murdered using the bloody billhook that had been left behind.  Forensic science was virtually non-existent at the time and the magistrates had no idea about who might have committed the crime.

Rather than letting the crime remain unsolved however, the magistrates were urged to consult Jacques Aymar. Though actually a stonemason, Aymar had become fairly famous in the area for his skill as a dowser. While dowsing had largely faded into obscurity by the 17th century, local stories quickly spread over Aymar’s success in locating underground springs and other lost items. 

But his greatest fame came from his apparent success at solving crimes. Several years earlier, Aymar had reportedly used his dowsing rod to track down a thief who had stolen some clothes in Grenoble, France.   Not only did his dowsing rod identify the thief, Aymar reportedly tracked down where the stolen goods were hidden. According to another story, Aymar had used his dowsing rod to locate the body of a murdered woman and implicated the woman's husband (who promptly fled the parish).  

The Lyons magistrates asked permission of the Procureur du Roi to test Aymar and see if he could find the murderer. Not shy about proclaiming his ability to find the murderer, Aymar insisted that he could solve the crime if he and his dowsing rod could be taken to where the murder happened. In the wine shop, Aymar carefully dowsed the crime scene and concluded that three men were involved in the murder. After gaining his impression of the killers, he left the wine shop and began tracking his prey across town. Following some impressive guesses, he began wandering into the countryside pointing out spots where the killers had slept, ate, etc.    

Although Aymar convinced some of the skeptics, the Procurateur General demanded that he be tested further. The local comptrollers, who likely had a vested interest in proving that Aymar was genuine, conducted several tests in which he allegedly "found" the murder weapon where it had been hidden. Since the available account fails to provide many details, it is hard to decide how rigorous the testing actually was.  

In any event, Aymar passed the tests with flying colours and was assigned a team of archers to help him arrest anyone who might be implicated by his dowsing. Following a lengthy search, Aymar's dowsing rod led him to a jail in a neighbouring town where, after securing permission to test the inmates, identified one hunchback prisoner as being involved in the murders. The prisoner, who had been arrested for stealing at a local fair, vigorously denied committing the murders or ever visiting Lyons. While Aymar offered to search for the other two killers, the hunchback prisoner was taken to Lyons for further interrogation.

Given that torture was still allowed in 17th-century France, that interrogation included a lengthy session on the rack and the prisoner was "persuaded" to confess. Not that he admitted to the actual murders, just to being a servant to the other two killers who were still at large. Aymar's attempt at locating them failed to turn up any leads and he concluded that they had fled the country. On August 30, 1692, the hunchback was broken on the wheel in the Place des Terreaux in the heart of Lyons. While there was no physical evidence linking the convicted man to the murders for which he was executed, his confession was deemed to be proof enough.

With the reputation Aymar gained after the Lyons case, the Prince de Conde took a personal interest in proving whether or not he was genuine. After ordering Aymar to Paris, the Prince arranged a new series of tests that would be far more rigorous than anything that had been tried on him before. In one of these tests, five holes were dug in a garden. One hole contained gold, one contained silver, silver and gold were placed in a third hole, copper in the fourth, and the fifth hole contained nothing but stones. Aymar failed this test miserably.

The Prince then sent Aymar to Chantilly to discover who had been stealing trout out of the ponds in a park. After carefully investigating with his dowsing rod, Aymar implicated one of the park's keepers who emphatically denied the theft. Seeing that Aymar was convinced of his guilt, the hapless keeper promptly fled (he likely heard what happened to the hunchback). To test Aymar further, the Prince arranged for a peasant, selected more or less at random, to be brought in as a suspect along with a young boy who was supposedly the keeper's son. When Aymar confirmed that they had both been involved in the theft, the Prince had all the proof he needed. Since the peasant and the boy were chosen at random (and the boy had not even been in Chantilly when the theft occurred), Aymar was sent away in disgrace.  

Other members of the French government decided to test Aymar as well. One of them, the Recorder of the King's Council, smashed a window in his house and called for Aymar to find the valuables that had supposedly been stolen. Not only did Aymar report that the thief had entered through the broken window, he also indicated another window that the thief had used to leave. Since no robbery had actually happened, that was enough for Aymar to be kicked out of the house as a fraud. After several other humiliating failures, Aymar left Paris and returned to Grenoble.

While Aymar's reputation for accuracy had taken a serious hit due to his failures in Paris, he was still famous enough to be used in other cases, including the notorious anti-Huguenot campaign to root out religious heretics (no word in the record on how successful he was there).   After that, he faded into obscurity with no details of his later life being available. Though Jacques Aymar helped popularize dowsing to France, his success as a crime-solver seems largely limited to the Lyons case. Even there, whether he actually identified the right man or not is debatable at best.

According to Sabine Baring-Gould in her classic book, Curious Myths of the Middle Ages ( which is still a must-read), dowsers seem particularly vulnerable to self-deception, especially since the actions of the dowsing rod are largely influenced by unconscious motor actions. In her own examination of the Aymar case, Baring-Gould was perhaps more charitable than modern skeptics would be and suggests that he may have genuinely believed in his own dowsing ability but that this confidence faded when subjected to actual rigorous testing. The history of dowsing is filled with examples of dowsers using anecdotes as proof of their success while failing completely when investigated by actual skeptics.  

In Aymar's case, what distinguished from virtually all other dowsers who tried and failed to prove their abilities was the fate of the man he identified as being guilty of the Lyons murder. Though the prisoner he identified confessed to the crime, the fact that his confession was extracted by torture makes it completely worthless as evidence. While dowsers have come and gone since Jacques Aymar's time, they largely confined themselves to less ambitious tests such as finding water or underground treasures.   

For the most part anyway. As JREF readers are no doubt well aware, a controversy over the use of dowsing tools to detect landmines has recently sprung up along with the bizarre decision by security forces in Iraq to purchase the devices for use in protecting troops. That people are still relying on dowsing to make life-or-death decisions centuries after Aymar's debacle demonstrates the need to be more vigilant in protecting people from the harmful consequences of sheer gullibility.


Romeo Vitelli, Ph.D. is a psychologist in private practice in Toronto, Canada. He is an active blogger and a regular contributor to the Huffington Post and Psychology Today. Check out his blog,Providentia.