A friend was involved in a car accident. The police came to her house, but she had a drink before they arrived. She was breathalysed and arrested and has now been prosecuted for drink driving. How can the police do this when she had alcohol after the accident?
To obtain a conviction for drink driving the prosecution must show that the motorist’s alcohol level was over the limit at the time she was driving. The police forensic experts can carry out what’s called a “count back” calculation. By working out the amount of alcohol consumed by your friend after she arrived home and deducting it from the intoximeter reading, they can calculate what her alcohol level must have been when she was at the wheel. If that level is over the limit then she can indeed be prosecuted and convicted.