One of my employees was stopped by the police outside his home as he was parking his car. Stupidly he had an open can of beer in his car that he was drinking from. the police did not wait 20 mins before giving him a roadside test. 1 hour later he blew 42 on the evidential machine. My question would be if he had only just drank a can of lager, the policeman literally took it off him, that alcohol would not be in his system at the time of driving. Is there a calculation an expert could do to see if the alcohol from that drink was removed from his reading at the station would be enough to bring him under 40. technically that alcohol was not in his system when he was driving. He only travelled 400m from a take away restaurant to his home and to lose his license over 3mg seems very harsh.