Forensic laboratories analyze solid and liquid samples for the presence of controlled substances. To meet accepted forensic standards the positive identification of a controlled substance requires two positive results from two diverse analytical methods. The most common drugs analyzed are marijuana, cocaine, methamphetamine, amphetamine, heroin, prescription drugs, and designer drugs. Drug analysis sections generally assist with the investigation of clandestine drug labs.
FIREARMS AND TOOLMARKS
Firearms and Toolmarks Sections are responsible for the comparison of firearms, cartridge cases, fired shotshells, projectiles, and other evidence that may be associated through toolmarks. Toolmarks result whenever two items come into contact with one another with sufficient force such that one or both of the items bear markings resulting from the other item.
The most important method utilized in the Firearms and Toolmarks Section is comparison microscopy which allows two items to be viewed simultaneously. Evidence projectiles, cartridge cases, or other items bearing toolmarks are compared to known items in order to determine consistency or inconsistency in both class characteristics and individual characteristics. Other examinations performed by firearms and toolmarks examiners include functional testing of firearms, distance determinations, and serial number restorations.
Serology/DNA sections of a forensic lab examine physical evidence collected through medical-legal and/or crime scene investigations to determine the presence of body fluids such as blood, semen, and saliva. The analysts compare the DNA profiles obtained from evidence body fluid stains with known DNA profiles of submitted known standard samples to identify likely sources of the unknown body fluid stains.
The Trace Evidence section examines crime scene physical evidence that is not analyzed by other sections, including:
- Glass fragments
- Gunshot/explosive residues
- Footwear & Tiremark
- Tape & adhesive
- General chemistry
- Precious metals
- Crime scene
- Evidence chain-of-custody
- High & Low Explosives
- Gunshot Residues (GSR)
- Natural &, Synthetic Fibers
- Human & Animal Hair
The Trace analyst must often develop unique approaches and combinations of analytical techniques to fully analyze the complex and varied submitted evidence.
LATENT PRINTS ANALYSIS
Latent print analysts examine suspected fingerprint evidence. Each finger and thumb is unique to an individual and no two prints have ever been found to be exactly the same from two different people. Also, palm and footprints are also unique to each individual. There are approximately 75 to 200 characteristics on a finger or thumb. The analysts use a variety of techniques --such as carbon powder dusting, super-glue and ninhydrin spray techniques, amido-black print visualization, and argon laser identification --to identify and match prints.
AUTOMATED FINGERPRINT IDENTIFICATION SYSTEM (AFIS)
One of the latest innovations in crime analysis is the Automated Fingerprint Identification System (AFIS), which is a computerized system that stores the identifying characteristics of more than 4.8 million individuals currently on file in the DPS Crime Records Service. AFIS sections also perform systematic computer searches of unknown fingerprints by optically scanning a print and comparing it with those on file. Prior to AFIS, fingerprint searches had to be done manually, making it an impractical, time-consuming process to compare an unknown print to the millions of known prints on file.
A Questioned Document Examiner examines original handwriting specimens from a variety of crimes, including but not limited to forgeries, suicide/homicide, threatening correspondence, fraudulent documents, sexual assault, etc. Other types of analysis include: typewriter examination (paper fiber transfer, wear patterns, and fracture patterns), photocopier comparisons, and ink comparisons (both destructive and non-destructive), rubber stamp comparison, trash bag comparisons, latent writing restoration, and obliteration restoration. All questioned QD exhibits must be accompanied by known standards (or exemplars).
Toxicology Sections of crime laboratories analyze body fluid in order to detect drugs in investigations related to driving while intoxicated (DWI), sexual assault, homicide, and drug overdose. Immunoassay screening of blood and urine detects drug classes present in a sample. Specific drugs from within the drug class detected are identified with confirmation analysis by GCMS (gas chromatograph/mass spectrometry) or LCMS (liquid chromatography/mass spectrometry). Analysis may include determination of the drug concentration in the blood for interpretive purposes.
BREATH AND BLOOD ALCOHOL TESTING
GFI can provide experts to review results of breath and blood alcohol testing to include:
- How testing was conducted
- Instrumentation used
- Instrument calibration history
- Training and certification by instrument operators
- Laboratory analysis of breath/blood alcohol evidence