why did he apply for a visa in the first place,very silly of him,the US customs have NO access to the british criminal record system and thousands of people with records enter the usa every year with them,only people with high risk catogory are denied entry to the usa,not someone who was silly 20 yrs ago,i doubt whether the customs would know his visa was turned down,but you never know,if he has paid for a ticket already then i would take the chance,he will only be sent back,not put in prison.