The death of Phar Lap - Australia's greatest sporting mystery - has finally been solved

It can now be revealed that scientific tests using breakthrough technology have uncovered evidence the legendary racehorse was poisoned with arsenic just hours before his 1932 death in the US. The startling revelation adds credence to the theory Phar Lap was killed on the orders of US gangsters, who feared the Melbourne Cup-winning champion would inflict big losses on their illegal bookmakers. Scientists used a US synchrotron, or particle accelerator, to unlock the 74-year-old riddle of Phar Lap's mysterious death. The proof lies in Phar Lap's hair.

A scientific report shows a large dose of arsenic was ingested by Big Red about 35 hours before his agonising death in California on April 5, 1932. "The arsenic in the hair structure is consistent with a single large dose of arsenic," the report says. The exact cause of his death was never proved, with suggestions ranging from the foul play theory to acute bacterial gastroenteritis.

But evidence of an arsenic overdose has been uncovered by scientists bombarding a strand of Phar Lap's hair with a beam of intense light. "We've made observations which could be explained by poison," Australian Synchrotron Research Program scientist Dr Ivan Kempson said. "We can't explain it by any other way."

Dr Kempson and Museum Victoria's Dermott Henry made the Phar Lap breakthrough by searching for minute traces of chemicals in the structure of Phar Lap's hair. Hair incorporates blood products and these can provide a timeline of exposure to toxins that can be unlocked using synchrotron technology. In 2000 the technology was used on six strands from a lock of Beethoven's hair to identify the cause of his illness and death - lead poisoning.

The latest CSI-style hunt to find what killed Phar Lap began in February last year when a sliver of hide was cut from his preserved skin. The 2mm square sample was cut from beneath the mane. A whole hair was then removed from the sample hide and analysed at a synchrotron outside Chicago in June last year and June this year. The tests revealed a high concentration of arsenic. "The arsenic in the hair structure is consistent with a single large dose of arsenic between one to two days prior to death," the scientists' report says.

The arsenic stretched about 900 microns along the hair from the root bulb, with a potentially deadly concentration found between 450 microns and 500 microns. Assuming a growth rate of 1cm a month, the scientists estimated Phar Lap was poisoned 35 hours before he died. Tests on two more hairs produced the same results. The behaviour of arsenic in the hair strand was also consistent with results from a test on the hair of a pig that had been poisoned with arsenic.

There have been many theories on what caused the giant five-year-old's agonising death, including accidental poisoning from lead insecticide. But many, including Tommy Woodcock - Phar Lap's devoted strapper - remained adamant the champ had been murdered by US racing and crime interests who feared an unbeatable outsider. It seems that he may have been right...