Jockey William Carson faces a possible riding ban of up to six months after testing positive for a metabolite of cocaine.
Carson, the 29-year-old grandson of five-time champion and multiple Classic winner Willie Carson, is due to attend a British Horseracing Authority disciplinary hearing on Thursday.
The case relates to a positive sample taken at Lingfield in March.
A statement from the governing body read: “The independent disciplinary panel of the BHA will convene on Thursday September 26 2019 to consider whether or not William Carson is in breach of the Rules of Racing due to the presence of banned substance benzoylecgonine, a metabolite of cocaine, in a sample collected from Mr Carson at Lingfield racecourse on March 27 2019 when a licensed jockey.”
BHA guideline penalties for a first positive cocaine test stipulate a ban “at the top of the range” between one month and six.
Carson has ridden more than 450 winners, but none from just 18 rides this year. His highest-profile success came aboard Regal Parade in the 2008 Ayr Gold Cup.