CHEMISTRY SECTION

 

The Chemistry Section of the crime laboratory analyzes evidence for the presence of cannabis and controlled substances as defined under the Illinois Compiled Statutes, Chapter 720, Acts 550 and 570.

 

Cannabis plant

The laboratory receives evidence for drug analysis in a variety of forms including plant material, powders, liquids, tablets, capsules and paper. The most common type of drug identified in the laboratory is cannabis (also known as marijuana or pot). The second and third most common drugs identified are cocaine and heroin respectively. Some other drugs commonly encountered in the laboratory include hydrocodone/acetaminophen mixtures (Vicodin®); benzodiazepines e.g. alprazolam (Xanax®), clonazepam (Klonopin®), diazepam (Valium®); hallucinogens including lysergic acid diethylamide (LSD), psilocin (found in “magic mushrooms”); ecstasy-type drugs including 3,4-methylenedioxymethamphetamine (MDMA), 3,4-methylenedioxyamphetamine (MDA); anabolic steroids including testosterone, stanozolol, nandrolone decanoate.

 

The drug analyst has to first weigh the sample without packaging. This is achieved using an electronic balance. Samples received in the laboratory can be as small as a residue amount that is visible by eye, but not conducive to weighing. They can also be very large.  The laboratory has received on occasion bales of cannabis (about the size of a microwave), and “bricks” of cocaine (about the size of a hard-cover novel).

 

After weighing the analyst then has to test the sample. At a minimum one preliminary test and one confirmatory test has to be performed to be able to make an identification.

 

Examples of preliminary testing include color tests – wet chemical testing; microcrystalline tests – using a polarizing light microscope (PLM); ultraviolet-visible spectrophotometry – measuring the absorbance of ultraviolet light by the sample dissolved in a liquid; thin layer chromatography – separating components of a sample on a chemically coated glass plate; gas chromatography – volatilizing a liquid preparation of the sample and separating components of the sample.

 

Gas Chromatograph-Mass spectrometer (GC-MS)

Confirmatory tests include mass spectrometry – breaking molecules into reproducible fragments

and infrared spectrometry – measuring the degree of transmission of infrared light through a sample. The data produced by both of these methods is called a spectra and is akin to a chemical fingerprint. For an unknown spectra to be identified as a controlled substance it has to be compared to a known standard (purchased from a chemical supplier, with a certificate of authenticity, that has been verified in the laboratory by comparing its spectra to published data before use in case work) run on the same instrument.

 

For cannabis in the plant material form a microscopical confirmatory test can be performed. This involves examining the unknown substance under a microscope and observing for the presence of distinct morphological features.

 

On occasion the section receives samples that despite thorough testing are not found to contain a controlled substance. Some examples of commonly identified non-controlled substances include baking soda, soap and vitamins.

 

 

CRIMINALISTICS

 

The Criminalistics Section evaluates and analyzes evidence for the presence of fingerprints, palm prints and footprints.  Any one of these types of prints can be formed by the impression of the friction ridges (raised portion) present on skin.  The impression left can be made by the natural secretions from sweat glands in friction ridge skin, referred to as a latent print. A latent print is a crime scene print.  Normally it is invisible, but not always.  Processing allows the print to be visualized.  Or they can be made by ink or other materials transferred from the peaks of the friction ridge skin to a relatively smooth surface, referred to as a patent print.

 

Two types of evidence are typically submitted:  lift-cards that have latent prints taken from a crime-scene, and objects to be processed at the laboratory for the presence of latent prints.  The section receives a variety of types of evidence for latent print processing.  Some examples include:  paper, (e.g. checks, notebooks, letters, money); plastic, (e.g. plastic bags, credit cards, bottles); glass, (e.g. bottles, mirrors); metal, (e.g. guns, knives, cash registers).

 

The composition of an object will determine which processing technique will be utilized to develop latent prints.  There are a variety of chemical and physical methods that can be used including superglue fuming, luminescence (laser), dye staining, powdering, ninhydrin and physical developer.  Many of these techniques can be used in tandem, for example, a plastic bag would first be superglue fumed then processed with Rhodamime dye. 

Fingerprint Record

After the analyst has processed the evidence to preserve and develop prints, the items are photographed.  The ridge detail observed in the photographs is then examined to determine if it is of value for comparison.  This evaluation process is also conducted on submitted lift-cards.  The first step is to compare any prints that are of value to the victim’s record fingerprints, or to anyone who had legitimate access to the crime scene.  Sixty to seventy percent of latent prints examined are identified as belonging to the victim.  The second step is to then compare any remaining unidentified prints to the suspect’s fingerprint record.  The third step, if there are any remaining unidentified fingerprints, is to enter them into the Automated Biometrics Identification System (ABIS) (formely known as AFIS).

 

The Illinois State State Police database contains over 3 million sets of fingerprints from arrestees, job applicants, police officers and civil service employees in the State of Illinois. The laboratory also has access to the Federal Bureau of Investigation (FBI) Next Generation Identification (NGI) database. 

 

A search of the ABIS system will produce a list of persons whose fingerprint resembles the entered print.  The analyst will then obtain a copy of the original fingerprint record to conduct the comparison.  An identification is made when the examiner determines that there are enough characteristics that correspond in both the questioned and known print that allows the examiner to conclude they were made by the same person.

 

 

FORENSIC BIOLOGY/DNA

 

Forensic Biology is the area of the crime laboratory dedicated to finding and classifying body fluids and biological substances from crime scenes.  The forensic biologist takes detailed notes, performs tests and collects and preserves an appropriate amount of the evidence for subsequent testing.

 

Tests for body fluids utilize chemical, enzymatic and microscopical techniques.  The body fluids most commonly tested for in the laboratory are blood, saliva and semen.  “Presumptive” tests indicate a body fluid may be present.  Preliminary chemical tests for body fluids usually involve a color change.  A small amount of blood – as little as a 1 to 1 million dilution – creates a fast blue/green color change with the Tetramethylbenzidine (TMB) test.  The chemical is reacting to the iron molecule in red blood cells.  This means that there is an indication that blood is present, but there may be a few other alternative explanations, even if they are less likely.

 

Presumptive tests for saliva look for a chemical called amylase.  Amylase is an enzyme that begins breaking down starches in the mouth.  A small amount of the sample is placed in a gelatin that contains starch and is allowed to incubate overnight.  If amylase is present, it will begin working its way outward from the center well where it was placed, consuming the starch as it radiates out.  Since the chemical iodine will turn starch blue, an iodine solution is then added to the plate.  Where starch has been consumed, a clear circle is observed.  The diameter of the circle is proportional to the amount of amylase that is present, indicating saliva.

 

AP Press Out on Clothing

Acid phosphatase, or AP, is an enzyme that is found in many body fluids, but is at its highest concentration in semen.  This presumptive test also requires a fast change to the color purple.  The presence of semen, the male reproductive fluid, can be identified by either the presence of sperm cells or by the presence of relatively large amounts of Prostate Specific Antigen, also known as PSA.  Sperm are identified using a stain and visually observing them through a microscope.

 

Usually, evidence is not forwarded for DNA analysis unless a body fluid is identified.  Contact DNA from handled items is impossible to detect prior to expensive and time-consuming DNA testing.  There are four basic steps in the DNA procedure:  extraction, quantification, amplification, and detection.

 

The extraction procedure breaks open the cells containing DNA.  It is important to have the DNA in a liquid environment where it can flow and move, and thereby interact with other chemicals that are used to test it.  After the DNA is released into the water, the sample is purified and concentrated by removing excess water.

 

After the sample is extracted, the analyst determines if there is any DNA in the liquid, and if so, how much.  The reaction of the extract is compared to the reaction of a series of standards with known concentrations, called a serial dilution.  Based on this comparison, a rough estimate can be made about the quantity of DNA present.

 

Electropherogram

The amplification process, known as PCR (Polymerase Chain Reaction), targets specific areas of the DNA and makes many copies of it.  By looking at only 13 different locations in the DNA, enough characteristics can be identified so that it becomes highly unlikely the DNA is from two different randomly selected individuals.

 

In the final step, detection of DNA products, only the STRs (Short Tandem Repeats) of interest are observed because during amplification, a small chemical was added to the DNA copy.  This chemical will glow when a particular kind of laser shines on it.  The flash of light from the chemical is captured by a digital camera and is displayed as a peak on print-outs called “electropherograms”.

 

The DNA profile obtained from the crime scene sample can then be compared to the DNA profile from a known individual or it can be entered into a computer database called Combined DNA Index System or CODIS.  This database contains DNA profiles from convicted felons, from other crime scene samples, from unidentified human remains and from other sources.

 

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