Evaluating Alleged Drinking after Driving — The Hip-Flask Defence

Abstract

This two-part article examines the strengths and weaknesses of various ways of investigating claims of drinking alcohol after driving, commonly known as the hip-flask or glove-compartment defence. In many countries the onus of proof in hip-flask cases rests on the prosecution. With good co-operation from the police and timely sampling of body fluids, such as blood and urine for forensic analysis of ethanol, useful evidence can be mustered to support or challenge the truthfulness of alleged drinking after driving. The person's blood-alcohol concentration (BAC) can be compared with values expected on the basis of the amount of alcohol consumed after driving, according to theoretical Widmark calculations. The actual BAC measured is then adjusted for the additional amount of alcohol consumed in the after-drink. Double blood samples, that is, taking two specimens of venous blood about 30-60 minutes apart and looking at the magnitude and direction of change in BAC provides little or no more information than a single blood specimen. However, the relationship between alcohol in blood and urine is very useful in hip-flask cases whereby the concentration expected in the primary urine is compared with the concentration in the bladder urine voided. The concentration of alcohol determined in a second urine sample collected 30-60 min later gives supporting evidence in hip-flask cases. A graphical method, which entails plotting ethanol concentrations in blood and urine as a function of time provides a robust and practical way to investigate hip-flask defences. In the second part of the review, congener analysis is presented, which entails comparing the concentrations of n-propanol, isobutanol and occasionally other congeners in the alcoholic beverage allegedly consumed after driving with the volatiles present in the suspect's blood and urine determined by headspace gas chromatography.

Pharmacokinetics of reduced iso-α-acids in volunteers following clear bottled beer consumption

“…This may represent another method of performing alcohol congener analysis (ACA) to assist investigations into the source of alcohol in routine forensic casework and in after-drinking (or hip-flask) defence cases where the feasibility of claimed alcohol consumption prior and/or subsequent to a motor vehicle incident is in question [25][26][27][28].…”

Toxicology of Specific Substances

“…When methanol intoxication deaths are investigated, some laboratories will determine the concentration of formate in Another application of methanol in forensic medicine is in connection with the prosecution of drunken drivers, many of whom claim that they drank alcohol after driving ended, the so-called 'after drink' or hip-flask defence (Iffland and Jones 2003). Traffic offenders who are not apprehended by the police sitting behind the wheel have the opportunity to claim they consumed alcohol after driving, which is not always easy to disprove.…”

Highly sensitive gas chromatographic determination of ethanol in human urine samples

“…Urine analysis for the presence of ethanol or illicit substances was described previously with several (headspace) GC methods [7][8][9]. Our FID GC detection method can easily be used for direct injection of urine samples without any pretreatment.…”