Crime scene investigations involve several aspects of chemistry when analyzing forensic evidence. Forensic chemistry is a diverse field, involving analysis of samples ranging from human body fluids to car paint. Each forensic laboratory will have different analytical capabilities from general chemistry to specialty analysis.
Forensic Laboratory Analysis Includes General Chemistry Testing
Forensic chemists identify unknown chemical substances collected from crime scenes. According to the Federal Bureau of Investigation (FBI) Chemistry Unit, this may include such chemical forensic evidence as:
- dye packs from bank robberies
- pharmaceutical identification
- dyes and inks
- flammable fluids
- petroleum products
- gunshot residue analysis.
Specialized forensic analysts may also be involved in identifying hazardous materials used in the commission of a crime or a threat of danger. These investigators may identify various types of toxins, fuels and bomb materials that are collected as evidence.
Forensic Toxicology
Toxicology is one of the most well-known disciplines in forensic science. The Society of Forensic Toxicology identifies three distinct areas of toxicology analysis, and these are:
- post-mortem analysis to determine if medications or other ingested, inhaled or injected substances contributed to cause of death
- urine testing for employment or suspect evaluation
- human performance testing which include blood and Breathalyzer testing of athletes or suspects.
Forensic toxicology encompasses many scientific areas including analytical chemistry, pharmacology, biochemistry, physiology and pathology.
Paint and Polymer Analysis
Paint and polymer technicians test samples for traces of paint, adhesives, and other similar materials. Evidence often comes from investigations involving motor vehicles such as hit-and-run accidents. Violent crime cases like bombings, counterterrorism and espionage may also produce this type of evidence.
Two paint databases are used to help identify automotive paint samples. The FBI in the U.S. maintains a National Automotive Paint File which includes car paint samples from vehicles as far back as the 1930s. The International Forensic Automotive Paint Data Query Database was started by the Forensic Laboratory Services Division of the Royal Canadian Mounted Police. Known as PDQ, the database contains information on chemical and color composition of vehicle paints. Paint samples come from car manufacturers, body shops and junk yards. PDQ currently contains paint identification for 13,000 vehicles and over 50,000 paint layers. Many international police agencies contribute to the database including the U.S., Japan, Australia, and the European Union.
Metallurgical Analysis
Chemists trained in metallurgy identify metal components found in pieces of evidence. Bombing investigation often involve materials analysis for metals.
Forensic Chemistry
Forensic chemistry incorporates a variety of analytical techniques for evaluation of evidence. Criminal cases may be solved by identifying the composition of various materials such as paint and metals. Human body fluids often give toxicologists answers to cause of death or behavioral issues involved with alcohol or illicit substance intoxication.
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