Stable isotope analysis, often combined with trace elemental profiling and chemical composition measurements, is at the forefront of food forensics, a discipline that seeks to use modern analytical techniques and sophisticated statistical tools to establish the authenticity and origin of foods. Two properties of special interest for foodstuffs are the stable isotopic and elemental compositions of natural and manufactured products, which are controlled by a large number of parameters: geography and climate—will affect rainfall and temperature and hence the localized hydrogen and oxygen isotopic composition of water, underlying geology and agricultural practices—will affect nutrient availability from soil to both plants and animals, and manufacturing processes—may introduce or remove components of a food and/or change the physical or chemical nature of some or all of these components. The Forensic Isotope Ratio Mass Spectrometry (FIRMS) network, in conjunction with the UK National Measurement facility, has produced an excellent Good Practice Guide (GPG) to stable isotope measurements.