Toxicologist

The Toxicologist is known as a doctor or professional in the field of identifying the presence of drugs in a subject.  They work for hospitals, laboratories, and police departments. You must have a thorough understanding of how internal organs produce enzymes, fluids and antibodies to be a Toxicologist.

Many tests can be performed that allow the toxicologist to identify whether or not drugs are present in the subjects system.  The three main tests are Thin Layer Chromatography (TLC), Gas Chromatography (GC), and Enzyme-Multiplied Immunoassay Technique (EMIT).

Gas Chromatography (GC)

This type of machine identifies illicit drugs by using stationary liquid to produce gas that rises into the surrounding environment. The sample is injected into a heated chamber, a constant stream of nitrogen gas flows through the injector forcing the sample through a series of seven columns that has a thin film of liquid present. The columns separate the gases and then the gases enter the detector that activates the recorder producing a recording that traces peaks and valleys based on a timed scale that identifies the concentration of drugs.

Thin Layer Chromatography (TLC)

A gel coated plate is spotted with a droplet of a blood sample from a suspect. Then the plate is placed into a closed chamber that is filled with a rising solvent. The greater the affinity of the substance the greater the speed it will travel up the plat. Then the plate is analyzed and compared with other plates that have been tested with substances similar to the one that has been tested.

Enzyme-Multiplied Immunoassay Technique (EMIT)

Enzyme –Multiplied Immunoassay Technique (EMIT) can be used for testing urine for a number of illicit drugs, the EMIT process consists of adding the antibody of the drug that the subject is being tested for.

Tests for alcohol represent a large number of incidents traffic and violence related crimes. The Toxicologist must test for alcohol by performing a breathalyser test, blood test, or urine test. The breathalyser is a well known device that is used frequently by Police Departments , it is almost a fail safe way to measure the amount of alcohol in a person’s breath and blood stream.

The Electronic Breathalyser

The Breathalyser test works by a chemical reaction that detects ethanol which is found in alcohol. When a subject blows through the tube of a Breathalyser test the chemical reaction detects ethanol in the air and compares it to a non toxic level. The chemicals used are sulphuric acid, silver nitrate, potassium sulphate and chromium sulphate. Sulphuric acid forces the alcohol to dissolve. The chromium sulphate and potassium sulphate react to the alcohol thus producing a small power surge. The silver nitrate speeds the reaction up for better charge detection. The electricity is then compared to a base reading and displayed on the screen for how much over or under the illegal rate of alcohol the subject is. 

References

Fisher, Berry A. (2004) CRC Press, Techniques of Crime Scene Investigation

Saferstein Richard (2007) Pearson Prentice Hall, Criminalistics, An Introduction To Forensic Science Tenth Edition 

Live strong.com (2010), How Does the Breathalyser Test Work? From source http://www.livestrong.com/article/30109-breathalyzer-test-work/