Forensic science is the use of technological and chemistry-based tools to gather and analyse evidence. The field includes tasks such as collecting fingerprints or testing for chemicals in blood and body tissues. Forensic scientists have a standard repertoire of chemical agents for their work. These agents can reveal evidence that may be hidden to the naked eye and provide clues to what happened at a crime scene.
Forensic scientists rely on four primary chemicals to reveal and collect fingerprints. These are iodine, cyanoacrylate, silver nitrate and ninhydrin. According to the Evident website, Eric Brown of Northeastern University and the Brazoria County, Texas, Sheriff's Department, these chemicals react to substances within the fingerprint, such as oil and sweat, making the print change colour so analysts can see it better.
Forensic scientists usually use iodine and cyanoacrylate--better known under the brand name Super Glue--by heating them to create fumes. They use silver nitrate and ninhydrin as a spray or dip. Other chemicals used for fingerprinting are diazafluoren 1, or DFO-1; rhodamine; ardrox; sudan black; thenoyl europium chelate, or TEC; and acid fushin. These chemicals help develop fingerprints on more porous surfaces or enhance prints already produced by other chemicals, by dying and stabilising the prints.
Fluorescein causes a chemical reaction between oxygen and the haemoglobin present in blood. This chemical is useful for fine blood stains and smears, according to the Latent-Prints website.
Another chemical used for blood evidence is luminol. This chemical reacts with iron in the blood. Luminol can reveal blood evidence even if someone has tried to clean the blood up.
The forensic scientist sprays these chemicals on the suspect area and observes the area to see if fluorescence occurs.
Luminol has limited use in forensic science, in that other chemicals like bleach can produce the same fluorescence as blood, according to Simon Lewis, associate professor at Deakin University.
Forensic scientists use common chemicals like hydrogen peroxide and alcohol in combination with the other chemicals at their disposal to produce better test results or speed reaction times. They also can use these chemicals as disinfectants; for instance, bleach can sterilise work areas or forensic tools.
Forensic scientists also may use acids to perform work like revealing etchings on metal. The fact that forensics requires the use of so many chemicals is why anyone interested in a career in forensic science must take chemistry courses.