Dr Margot Bolster, the assistant State pathologist, carried out a postmortem and told his family at an inquest in Cork that he would have been “deeply comatose” following the fall and “wouldn’t have known anything". 

Dr Bolster said Michael died of a catastrophic brain injury complicated by swelling with cerebral infarction due to a horse-riding accident. He had suffered multiple fractures of the skull in the fall. Dr Bolster said her findings were consistent with a fall from a horse.

Cardiac first responder with the Order of Malta, William Sweeney, said it was his duty on the day to cover the last fence of the racecourse.

In his Garda statement Mr Sweeney recalled that he he manned the last fence many times. He felt that “something seemed off” on the day of the incident.

“The horses were coming down the straight towards the last fence. I have a clear memory they were coming. I remember they were really pushing it, and recall saying, ‘there will be trouble here.’ 

"The horses reached and cleared the fence. I saw two horses fall a distance away from the fence, and then I saw a third horse fall immediately after the fence. My focus was on the third horse.

"The horse had fallen onto the rider, whom I now know to be Michael O'Sullivan, and until it was safely removed and he had been on top of him, kicking in panic."

Mr Sweeney said they took up position and secured Michael O'Sullivan's head.

“The head medical doctor from Kildare, moments later, she instructed me to keep securing the head while she carried out an assessment.

"I was instructed by the doctor to remove Michael O'Sullivan's helmet, which I did, and to apply pads and pressure to his ears which were bleeding. I followed the doctor's instructions and maintained this position until the arrival of the higher ambulance helicopter. 

"To me, we felt like 10 or 15 minutes before the helicopter arrived. Once the helicopter arrived, I was asked to assist with getting into the helicopter, which I did.

"When I said, 'There will be trouble here,' what I meant was from experience, sometimes we can anticipate the fall may be coming due to the horse's approach.” 

'Very experienced jockey'

HSA inspector Justin Walsh prepared a report on the incident for the coroner. He stated that Michael was a “very experienced jockey” who was wearing the appropriate equipment on the day he sustained fatal injures. No breaches of healthy and safety were identified. The inquest heard that risk was something that could not be fully eliminated from horse racing.

Jennifer Walsh, raceday operations manager with the IHRB, said the course had been fully inspected on the day of the race. All of the appropriate veterinary checks were made. She said the weather was “fine, bright, and clear".

A through review of the incident was carried out by the IRHB.

Horse owner and trainer Gerald O’Leary said  the late Michael O’Sullivan had previously had success on his horse Wee Charlie. 

He said the seven-year-old horse was a “straightforward, sound horse with no vices” and that Michael was an “experienced rider".

Mr O'Leary said: “They (Wee Charlie and Michael) were a good team. I spoke to Michael on the phone before the race. He said, ‘We have a good chance.’ I didn’t speak to him again.” 

IHRB veterinary officer Nicola O’Connor said Wee Charlie was deemed “fit to race” on the day having been examined that morning. There was no history of previous injury or lameness.

Jockey Sean Flanagan participated in the race in which Michael sustained fatal injuries. Sean fell off his own horse on the last jump of the race. He said that “a number of other horses and jockeys also fell” with most falling independently. He spotted Michael on the ground with his horse beside him.

He stated that a doctor was tending to Michael and that the jockey was subsequently airlifted to hospital. The race was abandoned.

Another jockey who participated in the race, Tiernan Roche, said there was “nothing out of the ordinary” on the day. He said Michael “just seemed very unlucky".

Dr Jennifer Pugh, chief medical officer with the IHRB, said Michael was wearing an appropriate helmet on the day of the fall.

She said a through review of the incident had revealed that Wee Charlie had become unbalanced, leading to the fall. She said the course was “in good order” on the day and that Michael was in compliance with all of the safety regulations as regards equipment.

Verdict of accidental death

A jury recorded a verdict of accidental death. Coroner Philip Comyn extended his sympathy to the family of the deceased following the death of the “up-and-coming" jockey. 

Mr Comyn said that, “more importantly”, Michael was a “much loved” young man who would be sadly missed by his family.

Denis Linehan, solicitor, addressed the court on behalf of the O’Sullivan family. He said the death had impacted not only on his family and the local community but also on the horse riding world — both in this country and internationally.

Mr Linehan stressed that medics at the racecourse were “heroic in their efforts” following the “unbelievable and terribly tragic accident". He also paid tribute to Dr Jennifer Pugh for the “humane” manner in which she had communicated with William and Bernie O’Sullivan following the death of their son.

Sgt Fergus Twomey and Justin Walsh of the Health and Safety Authority also offered their heartfelt condolences to the famly of the late Michael O’Sullivan.

Shot to public attention

Michael shot to public attention in 2023 when he won the Supreme Novices’ Hurdle at Cheltenham aboard Marine Nationale before going on to win the Fred Winter with Jazzy Matty.

Huge crowds attended his funeral at St John the Baptist Church in Glantane, Co Cork, in February of last year. William O’Sullivan told mourners that his son had his heart set on becoming a jockey from an early age. 

He said that although Michael had managed to receive a degree in agricultural science from UCD, he had it on “good authority” that his horse-mad son read the Racing Post during lectures.

Since his death Michael’s family have raised tens of thousands of euro for Brú Columbanus, a charity which offers free accommodation to families of seriously ill patients in Cork hospitals.