If the evidence of theft is strong, and proper procedure is followed, getting to a guilty verdict isn't going to be the issue. It's going to be the fair and appropriate sanction that'll be the battleground.

Fair chance the argument in mitigation will be that their judgement was impaired due to intoxicating liquor supplied by the company.

If there is no history of misconduct, I suggest shoot for a final written warning and restitution of the goods - and everyone will be a winner.
(Well, sort of).