Alcohol back calculation for road traffic investigations

Guidance on the reporting of alcohol back calculation cases where the time between the reported last drink and the incident of interest is less than one hour.



Back calculation is the process whereby a forensic toxicologist uses the concentration of alcohol in a blood or breath sample to calculate the concentration of alcohol in the individual’s blood or breath at some time before the sample was taken. This type of evidence appears regularly in road traffic investigations.

Published 8 May 2015