A forensic chemist is a scientist who works for a law enforcement agency or a private government organization. He or she is in charge of identifying and analyzing physical evidence gathered at crime scenes. A forensic chemist is an important part of the criminal investigation process, even if he or she does not participate in the actual collection of evidence. A forensic chemist may choose to specialize in blood typing, fingerprinting, chemical identification, or hair, soil, glass, and fiber analysis because forensic chemistry requires a broad range of knowledge. Forensic chemists work in the United States, Australia, and the United Kingdom, among other places.
Serology is the scientific study of blood typing and body fluids, and a forensic chemist who specializes in serology uses enzyme tests on samples of semen, blood, saliva, hair, or other bodily fluids found at a crime scene. The chemist can use the enzyme results to determine a unique DNA profile because enzyme compounds found in fluid samples are almost always unique to a specific individual. Investigators can use that profile to search a DNA database for a suspect or compare it to other potential suspects.
Because evidence samples may be contaminated with other substances, a forensic chemist who specializes in chemical identification may need to use analytical techniques to separate the chemical compounds of a sample. He or she will most likely use a gas chromatograph to separate compounds from other impurities in an evidence sample, such as dust or dirt. Based on the chemical compounds extracted, a chemist can then determine what a sample is and where it came from. Unidentified colored particles found on a victim’s body, for example, could be tested and identified as a specific brand and shade of paint. If the sample matches paint in the suspect’s home, for example, investigators could use that information to link him to the crime.
A forensic chemist may need mock trial courtroom experience as part of his or her job training, in addition to identifying and analyzing crime scene evidence, because he or she will typically have to testify as an expert witness in criminal cases and present his or her conclusions on the evidence to the jury. In general, he or she will compare the evidence to previous cases in order to provide an expert opinion on how the evidence implicates a suspect specifically. Even if the testimony is favorable to the defense, a forensic chemist must give unbiased, scientifically-based findings, even if he or she works in a law enforcement laboratory.