The condition of a track described as "horrendous" potentially caused a horse to fall at a Canberra racecourse, leaving its rider with a fatal head injury, a coroner has found.
Australian National University student Riharna Thomson, 22, died at Canberra Hospital in March 2017, three days after a horse named Chosen Prayer fell at Thoroughbred Park.
Coroner James Stewart found this week that the horse had fallen after fracturing its leg, "either by catastrophic bone failure or by being ridden on an inconsistent track".
In his findings, Mr Stewart said Ms Thomson had been, by all accounts, an experienced and skilled rider well and truly capable of handling Chosen Prayer.
She had been riding horses most of her life and worked for different trainers before joining Keith Dryden as a stable assistant at Thoroughbred Park about a year before her death.
One day in late February 2017, Ms Thomson rode Chosen Prayer, a six-year-old mare, on a synthetic surface known as Acton Track.
No one saw the horse fall but a tracking device, which recorded the animal's speed and heart rate, revealed it had been running at about 66km/h when it broke its front left leg.
Chosen Prayer's fall caused Ms Thomson to land on the track, most likely head first.
A veterinary examination conducted the next day found the horse, which had to be euthanised, to have been in "good body condition".
But Mr Stewart said there remained "important questions" about Chosen Prayer's behaviour prior to its breakdown, with the available evidence "silent" as to whether the animal had become unmanageable or difficult to manage.
He accepted that racehorses sometimes suffered from catastrophic fractures, whether they happened spontaneously or as a result of "micro-damage" to bone structures.
The coroner devoted much of his decision to the condition of the Acton Track, which WorkSafe ACT temporarily closed about two weeks after Ms Thomson's accident.
He said there had been multiple complaints about the state of the track, on which three horses, including Chosen Prayer, had fallen within a four-month period.
A track work rider and occasional jockey, who had about 10 years of experience at the time in question, described it as having been "horrendous and inconsistent".
Mr Stewart ultimately found the condition of the track was a potential cause of Chosen Prayer's fall.
He noted it had been "remedied" after the three horses fell, with no complaints made about it since.
Mr Stewart also said he approved of steps taken since the incident by the Canberra Racing Club, which said it had implemented a more formalised process to deal with any shortcomings associated with communication and documentation of safety issues at Thoroughbred Park.
