United Arab Emirates (UAE) rider Sh Abdul Aziz Bin Faisal Al Qasimi has been handed a record 20-year ban after the International Equestrian Federation (FEI) Tribunal found doping injections led to his horse suffering a fatal injury.
Castlebar Contraband had to be put to death after suffering an open fracture to its front right cannon bone during an event in France in October 2016.
The post mortem report showed the horse had been injected with Xylazine, which is used as a sedative, analgesic and muscle relaxant but is prohibited in competition.
FEI veterinary director Dr Göran Åkerström said the substance increased the risk of "catastrophic" injury.
The report revealed the horse had "multiple lesions with a highly targeted location, consistent with recent injections, demonstrating that the horse had been nerve blocked (desensitised) in training, and both before and during the competition".
"This desensitisation, together with osteoarthritis in the right front fetlock joint, resulted in stress fractures that ultimately caused the catastrophic injury," the FEI Tribunal said.
Al Qasimi's legal team argued that Xylazine had been used in the euthanasia process, a claim rejected by the FEI Tribunal, which accepted the explanation of the treating veterinarian.
The athlete has been suspended from the sport for 20 years, the strongest sanction in the history of the FEI.
Al Qasimi was given an 18-year ban for horse abuse and a two-year suspension for violating the Equine Controlled Medication rules.
He is banned from the sport until May 27, 2040 and has been ordered to pay a total of CHF32,000 (£26,300/$32,300/€29,500) – a fine of CHF17,500 (£14,400/$18,200/€16,100) and CHF15,000 (£12,300/$15,600/€13,800) towards the cost of the proceedings.
"This is a really great result for horse welfare and the fight against doping in equestrian sport," FEI legal director Mikael Rentsch said.
"We are very happy to see such a strong sanction handed down by the FEI Tribunal and it offers a stern warning to others that the Tribunal will not tolerate cases of horse abuse.
"This was a tragic case of a horse losing its life due to desensitisation and micro-dosing and, while we have had concerns that this has been ongoing for some time, this was the first solid evidence we have had of nerve blocking during rides as well as micro-dosing."