Forensic applications of stable isotope analysis: case studies of the origins of water in mislabeled beer and contaminated diesel fuel.

This paper describes the use of oxygen (18O) isotope analysis of water contained in two different materials--beer and diesel fuel--involved in the resolution of two separate cases. In the first case study, it was possible to demonstrate that a sample of beer labelled as premium brand in fact belonged to a cheap brand. The second case related to the contamination of diesel fuel from a service station. The diesel fuel contained visible amounts of water, which caused vehicles that had been filled up with it to become defective. For insurance purposes, it was necessary to determine the source of water. The delta18O values for the water of nearly all samples of diesel was close to the delta18O of local tap water at the filling station.