Forensic Chemistry is a broad discipline which performs identification and comparison of nearly any imaginable material on the basis of its physical and chemical characteristics, to establish its importance and its possible origin.
Since the entire world around us is made up of chemicals, this discipline covers an incredibly diverse array of materials encountered at crime scenes, ranging in severity from vandalism to homicide and incidents of terrorism. In fact, some materials are encountered so frequently during investigations that they are collected into defined areas of examination: fire debris, paints and polymers, glass, fibers, dyes, explosives, and gunshot residue are among the most common areas of examination, but cover only a fraction of the full breadth of materials that forensic chemists examine worldwide.
Often, the relevant material from a crime scene amounts to only a trace transferred by the perpetrator to the scene (usually without their knowledge) and sometimes also from the scene to the perpetrator. To detect such traces requires thorough examination of the scene. They are often invisible to the naked eye and demand careful collection from the scene, followed by meticulous search and recovery in a controlled laboratory environment.
Forensic chemists rely not only on powerful microscopes and steady hands, but also on a wide array of analytical instruments and techniques to generate enough information to characterize each recovered sample, and to seek out any possible physical or chemical differences between them. Successful forensic chemists possess keen observation skills as well as a broad knowledge of chemistry and of how different materials are made. Because many of the materials encountered in our world are mass produced, many different objects may have very similar composition, making the job of determining forensic significance difficult for the chemist.
Fortunately, technological advances have led to many field-portable instruments which can be taken directly to the scene. Through the involvement of forensic chemists, carefully designed databases may be coupled with the mathematical power of computers to statistically classify forensic samples right where they are encountered. In many countries, scientists are already working in tandem with front line officers, using these new tools to provide immediate intelligence to law enforcement as an investigation unfolds.
While this new approach to forensic chemistry is early in its development, it is gaining momentum quickly and promises to pave the way for a new generation of forensic chemists who help push the boundaries of what we can know, while ensuring that every answer given is correct and complete.