The only place that "beyond a reasonable doubt" is the standard is in a criminal court. Even in civil court, the standard is "preponderance of evidence". This isn't a court at all.  (not yet, anyway)  This is just a private racing organization. While a presumption of innocence is nice, there's nothing which mandates it for the internal affairs of a private organization.   If this rubs you the wrong way,  you should really be upset by mandatory drug testing for DOT covered employees. The same standard is used there, if you test positive, you are presumed to be an illegal drug user. There really is no way out of it if it was an accidental or malicious dose.