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Forensic Services Division


Drug Chemistry Unit

The Drug Chemistry Unit analyzes any substance seized in violation of laws regulating the sale, manufacture, distribution and use of abusive type drugs.  In a coordinated effort between the Drug Investigation Division and Forensic Services Division, clandestine laboratory cases are processed. 

Toxicology Unit

The Toxicology Unit conducts analysis of blood and other body fluids for alcohol, drugs or poisons, in conjunction with persons arrested for traffic charges (DUI) or to assist medical examiners in death investigations. The Breath Alcohol Unit administers and maintains Tennessee’s breath alcohol testing program. Scientists assigned to this unit certify and calibrate evidentiary breath alcohol instruments throughout the state. The staff is responsible for training law enforcement personnel as operators on the instruments.

Evidence Receiving Unit

The Evidence Receiving Unit receives, inventories, distributes and stores all evidence submitted to the laboratory.

Latent Print Examination Unit

The Latent Print Examination Unit provides analysis of physical evidence for invisible fingerprints and/or palm prints and comparison of latent prints developed with the inked impressions of suspects.

An Automated Fingerprint Identification System (AFIS) workstation is located in this unit, allowing unidentified latent fingerprints obtained from crime scenes or developed on evidence submitted to the laboratory, to be searched against the database of fingerprint records maintained by TBI. In addition, the latent print unit has the capability of submitting unidentified latent prints from major crime scenes to the FBI for a fingerprint database search.

Firearms Identification Unit

The Firearms Identification Unit's principle function is to determine if a bullet, cartridge case or other ammunition component was fired from a particular weapon to the exclusion of all others.  The science of firearms identification extends beyond the comparison of bullets to include knowledge of the operation of all types of weapons, the restoration of obliterated serial numbers on weapons and other evidence, the detection and characterization of gunpowder residues on garments and around wounds, the estimation of muzzle-to-garments distance and the detection of powder residues. In October 2002, a National Integrated Ballistic Information System for confirming bullets and cartridge cases became an integral part of the Firearms Unit.

Services Performed

Microanalysis Unit

The Microanalysis Unit examines and compares the evidence types described below:

Fire Debris Analysis
Debris from fire scenes is examined to determine the presence of an unconsumed ignitable liquid, which includes the products of refined oil (gasoline, kerosene, diesel fuel, etc.).  Alcohol and other flammable/combustible products can also be detected.  Ignitable liquids that have not been consumed by fire, washed away by water, or evaporated by exposure, are most often found remaining in materials that have absorbed them easily and retained them well.  These include carpeting, soft woods, fabrics, paper, soil and occasionally concrete.

Analysis of Gunshot Residue Kit
This analysis is used to determine the presence of antimony, barium and lead from hands of individuals who may have fired a gun.

Analysis of Gunshot Primer Residue on Objects
This analysis is designed to determine the presence of antimony, barium, and lead that were near a firearm when it was fired. 

Shoe Impression Comparisons
Shoe impression evidence at a crime scene can be present and recreated.

Explosive Residue
Explosive devices which have been detonated may be examined for the type of explosive contained in the device. All submissions much first go through an acceptance process by State Bomb and Arson to assure that a device is no longer functioning.

Tire Impression Comparisons
Tire impressions recovered from a crime scene or tire impressions on an object such as victim's clothing can be compared to known tires from a subject vehicle.

Paint Analysis and Comparisons
The analysis and comparison of paint evidence may be conducted on paint, liquid or dried, that may have been transferred from the surface of one object to another during the commission of a crime.

Glass Fracture Analysis/Order of Breakage
Glass is a rigid, durable material with variation in composition and application which renders it useful as associative evidence.  Glass fracture patters are unique; fractures caused by impact, heat, high velocity projectiles and glasscutters may each be distinguished.  Laboratory examination of recovered shards of glass may reveal the direction and sequence of breaking.

Glass Comparisons
When glass is broken, glass particles rebound and shower onto the hair and clothing of any individual in the vicinity.  Glass particles can also be embedded in the objects used to break the glass object.  Glass from the subject's clothing and body can be compared to a glass standard from the crime scene.

Fiber Comparisons
Individual fibers as well as larger textile constructions such as fabric, carpet and cordage may be characterized and compared to corresponding materials recovered from a suspect or his/her environment.  Laboratory analysis of fibrous trace evidence is based upon microscopic examination and comparison, in conjunction with instrumental methods.

Indented Impressions
Indented impressions are created when the writing, drawing, typing or printing upon a top sheet of paper imparts an indentation on the sheet(s) of paper immediately below the page bearing the intended image.

When two vehicles collide, or a vehicle strikes another inanimate object at a high rate of speed and if the speedometer needle is painted, an approximate speed at the time of impact can be determined.

Composite Imagery
The Microanalysis Unit provides Forensic Art Services including composite drawings of suspects, skeletal remains or age progression.

Tape Comparisons
A torn or cut end of tape recovered from a crime scene may be found to physically match the end of a partial roll recovered from the subject(s).

Physical Comparisons
The purpose of a physical comparison is to associate two or more items using individual characteristics (fracture matches) or class characteristics (size, construction and physical properties). 

Serology/DNA Unit

The Serology/DNA Unit performs identification and characterization of blood and other body fluids, namely blood, semen and saliva - liquid or dried, animal or human - present in a form to suggest a relation to the offense or persons involved in a crime.  This Unit also performs DNA Profiling, the capability to identify specific individuals by comparing biological samples left at a crime scene or from the body of a victim.  DNA Profiling is performed using the Polymerase Chain Reaction (PCR), Short Tandem Repeat (STR) DNA Analysis.

In February 2002, the TBI Combined DNA Index System (CODIS) Database became fully operational.  Advances in DNA technology represent one of the most significant forensic breakthroughs of the century by allowing the identification of a murderer or rapist based on trace amounts of biological evidence left at the crime scene.  The database was established nationally by the Federal Bureau of Investigation to enable crime laboratories to exchange DNA profiles for unknown subjects and convicted offenders.  The national index assists agencies in developing investigative leads since subjects can be searched against the file of convicted offenders.