Four-year-old bay mare Lina's Choice collapsed in trackwork near the winning post at a country NSW racecourse in February 2022.
Apprentice jockey Marina Morel was thrown over the horse's head and became trapped underneath the panicked animal as it thrashed around, unable to rise.
The 30-year-old suffered critical injuries and was airlifted to Sydney's Westmead Hospital, where she was put on life support while her mother travelled from France to be with her.
Four days later, the talented horse rider was declared dead.
Lina's Choice suffered a catastrophic injury and was put down, an inquest into Morel's death was told on Monday.
A key issue being explored at the inquest is the medical fitness of the horse when it collapsed at 7.30am on February 8, 2022.
Lina's Choice ruptured a ligament during training in March 2021, prompting horse trainer Brett Thompson to call veterinarian Jack Holman after noting she appeared to be lame.
Dr Holman recommended the horse rest in a stable for six weeks and 12 months in a paddock before returning to racing.
But Lina's Choice went back to work six months after the injury, counsel assisting David Kell SC noted.
Dr Holman wasn't concerned about the early return because he felt the injury would make itself known in training if it recurred, the inquest was told.
Thompson and his team found no signs of lameness or injury when closely monitoring the racehorse during the training, Dr Kell said.
An equine chiropractor told the inquest he similarly found no lameness when he examined Lina's Choice in the lead-up to the fatal accident at Gulgong in central western NSW.
But he had noted muscle tension and stiffness to be monitored.
A veterinary surgeon expert is expected to tell the inquest that a thorough veterinary examination would have found a stress fracture in the horse's leg weeks before the accident.
One of Thompson's employees reported being told that Lina's Choice had pulled up lame after her last race in Dubbo and should not have been racing on the day of the accident, Dr Kell said.
But the woman to whom she attributed the information denied having the conversation.
After Morel's death, Dr Holman reviewed literature that led him to conclude six months would have been an adequate recovery period for the partial rupture, he told the inquest.
The regulations surrounding a racehorse's return after injury are one facet of the processes and systems related to horse racing that will be scrutinised by the coroner.
Exploring and identifying potential shortcomings during the inquest may help prevent other deaths, Dr Kell said.
"It's important to find out what lessons can be learned from the death of Marina …. (so) maybe her tragic death will not have been in vain," he said.
With the assistance of an interpreter, Morel's parents followed the inquest proceedings via audiovisual link from France.
Both Thompson's training company and Racing NSW are legally represented at the five-day inquest.
