Hip flask defence

In places like the United Kingdom, a hip flask defence is a defence to an allegation of drink driving that a driver had consumed alcohol between the time of a vehicular offence, such as a traffic collision, and a breathalyser test, so that a positive result does not actually indicate that they were driving while intoxicated.

Though popular (in 1991, the defence was used in 90% of Swedish appeals against drink driving convictions), the hip flask defence is not always effective. It is possible to back calculate the amount of alcohol and prove an offence nevertheless.