Driven by forensic intelligence, illicit drug chemical profiling via Gas Chromatography-Mass Spectrometry (GC-MS) remains the leading approach that forensic scientists and law enforcement agencies pursue in a bid to counteract the ever-increasing drug epidemic. An alternative approach for forensic drug investigations that delivers intelligence at a more specific level than that of chemical profiling is isotopic profiling via Isotope Ratio Mass Spectrometry (IRMS). The analysis of selected stable isotopes (18O:16O,15N:14N, 13C:12C and 2H:1H, for example) that compose drug molecules has been suggested as a credible technique that can aid in forensic drug investigations. This research, consisting of four individual projects, was designed to investigate the potential of using isotopic profiling for source, synthetic procedure and batch linkage or discrimination of selected designer drugs/Novel Psychoactive Drugs (NPDs).