The Forensic Chemistry section has combined the responsibilities of the Drug laboratory section and the chemistry duties of Trace Evidence. By doing so, Forensic Chemistry will be able to do:
1. DRUG TESTING
The Forensic Drug Laboratory was created by the Westchester County Medical Examiner in 1974. Previously, the work product was one of the functions of the toxicology section. At the present time, our lab performs examinations on powders, liquids, tablets and capsules, and vegetable material looking for the presence or absence of controlled substances. We accept evidence submissions from over fifty different law enforcement agencies in Westchester County. Our lab analyzes over 2500 drug cases per year.
When an analyst accepts a case, the analyst takes notes describing the contents of the case and begins to prepare a written report. The next step is usually taking a weight of the item or items submitted. This helps determine whether a misdemeanor or felony charge will be applied. The analyst then performs a color test on a small portion of the drug. This test while not specific, can give the analyst an idea of the category of the drug present. The analyst may then perform a microscopic crystal test. These tests are performed using a polarized light microscope and the tests are capable of identifying the drug present.
Gas Chromatograph / Mass Spectrometry
The Gas Chromatography / Mass Spectrometer (GC/MS) is a
sophisticated instrument that can not only separate chemical components from
each other, but can also identify what each component is.
After all the testing has been completed, a report is generated for the submitting agency and the District Attorney's Office. The evidence is resealed and stored until it is picked up by the submitting agency. All material pertinent to the case is saved awaiting a possible trial, and is archived.
Links To Forensic Sites
Forensic Chemistry deals with the chemical analysis of a variety of types of physical evidence. These include suspected accelerants from arson debris, gunshot residue on the hands of a shooter, lubricants and noxious chemicals such as tear gas and capsaicin (pepper spray). The type of cases typically examined include arsons, homicides, assaults, bank robberies, and vandalism.
Arsonists may use a variety of possible accelerants to set a fire. During the examination of a potential arson scene, cause and origin investigators collect fire debris that they believe contains residues of these accelerants. The debris is placed in airtight containers to avoid possible loss of the volatile components and is transported to the laboratory for analysis. The Forensic Chemistry section utilizes Gas Chromatography-Mass Spectrometry to identify traces of ignitable liquid residue in these samples. The forensic chemists will often have to concentrate the small amounts of residue. They accomplish this by adsorbing the accelerant residue onto activated charcoal strips. The concentrated accelerant is then eluted off the strip by dissolving in a solvent.
Gun Shot Residue
In addition to arson debris, this section also examines evidence associated with shooting cases. When a firearm is discharged, gases are generated containing burned and unburned components from both the propellant and primer of the cartridge. This material may deposit itself on the clothing of a victim or on the hands of the person firing the weapon and is referred to as gun shot residue. The Forensic Chemistry laboratory utilizes a state of the art Scanning Electron Microscope (SEM) fitted with an Energy Dispersive Spectrometer (EDS) to examine tape lifts taken from the hands of suspected shooters. This automated instrument is capable of searching several hundred microscopic fields overnight for the presence of small primer residue particles. When a particle is located, its coordinates are recorded and the particle is analyzed using the EDS unit. If a particle is identified as containing barium, antimony, and lead it is classified as primer residue. The particle's coordinates can also be recalled and it can be photographed using the SEM.
Noxious chemicals such as tear gas and capsaicin can be identified using the gas chromatograph-mass spectrometer. Tear gas is commonly found as a component in dye packs used by banks to identify suspected bank robbers and may be detected on an individual's clothing after the dye pack has exploded.
The Forensic Chemistry section can also assist in sexual assault investigations by examining traces of lubricants used by suspects in rape cases.