A dram-shop claim turns on whether the club served someone it knew, or should have known, was visibly intoxicated - or a minor, where no intoxication has to be shown at all. The defence is a record made at the time. Patrons are logged by a tag - a table, a seat, a wristband number - never a name. A tag that is cut off gets nothing more that night, and anyone who looks young is served only after their ID is checked.

42 states and DC have dram-shop laws: a bar can be sued for harm done by a patron it served while visibly intoxicated, or served underage. Delaware, Kansas, Louisiana, Maryland, Nebraska, Nevada, South Dakota and Virginia have no general one - but a licence can still be lost, and some states make serving the visibly intoxicated an offence. Most courts ask whether the bar knew or should have known; following the state's server-training rules is a recognised defence.