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Greeley/Weld County Forensic Lab
 The
Greeley/Weld County Forensic Lab provides several scientific services to the
Weld County Sheriff’s Office and the Greeley Police Department. These are in the
categories of crime scene, fingerprint, digital evidence and chemical analysis
services. The chemical analysis services have been accredited by the American
Society of Crime Laboratory Directors / Laboratory Accreditation Board (ASCLD/LAB)
since 1991.
Footwear and tire impression evidence is commonly found at crime scenes.
Crime scene investigators will document these impressions through photography
and casting or lifting techniques. It is the job of the expert in the
Greeley/Weld County Forensic Lab to compare shoes or tires submitted to these
photographs, castings and lifts to determine if they made, could have made, or
did not make the crime scene impressions.
At crime scenes the specialists in this area work with investigators to first
identify evidence. Then it is the crime scene specialist’s responsibility to
document, collect and preserve all the evidence at major crime scenes. They must
diagram crime scenes and account for all the evidence gathered. The
quality of their work and their testimony in court is crucial to the
admissibility of the evidence gathered.
Fingerprint comparison is probably the oldest recognized forensic specialty.
However, before a comparison can be made, fingerprints must be found, visualized
and documented. Many specialized methods have been developed to visualize
fingerprints on the many surfaces needing fingerprint processing. In addition to
the fingerprint powders that are available, there are many chemical methods used
to treat surfaces. Most of these chemical methods are used in conjunction with
an “alternate light source” to enhance the detail and contrast of a fingerprint
on a surface. Prints visualized with powders are “lifted” with tape and placed
on a contrasting background
for
examination. Prints visualized using other methods must be photographed to
scale, and the photos used by the examiner for comparison. A fingerprint
comparison expert must then judge the quality and detail in an unknown print
before a comparison can be made. Using high-resolution digital photography and
image enhancement software, an examiner
 can digitally “remove” things like
repeating patterns or interfering colors in the surface the fingerprint is
photographed on to produce a better quality fingerprint.
Digital evidence is like fingerprints. Investigators don’t know what they have
until an expert examines their evidence. The digital evidence expert must first
preserve the original evidence by making an exact copy or “image” without
altering the original. This copy is then subjected to file searches for evidence
of a crime, and file restoration, if the suspect may have deleted files that are
evidence. Any digital device can be “examined”, not just computers. The need for
this service to law enforcement has grown dramatically as digital devices are
used by all of society as well as criminals.
 Chemical
analysis services primarily use infrared spectroscopy (I.R.) and gas
chromatography/mass spectroscopy (GC/MS), as well as microscopic examinations
and photography where appropriate. The majority of cases requiring chemical
analysis involve identifying controlled substances (illegal drugs). Suspected
arson cases require analysis for ignitable liquids that can be used to
accelerate the progress of a fire. When investigating hit-and-run cases,
investigators often find that paint was transferred from a suspect’s vehicle to
a victim’s vehicle, from a victim’s vehicle to a suspect’s vehicle, or both
ways. In burglary investigations involving forced entry, paint can be
transferred from a windowsill or other painted surface to a burglary tool.
Comparisons can be made between known paint samples and unknown samples by
analyzing their organic and inorganic chemical compositions.
The services provided by the highly trained personnel in the Greeley/Weld County
Forensic Lab are as comprehensive in the specialty areas described above as
larger labs. The goal of the lab is to provide quality services that meet the
needs of the criminal justice system in Weld County. Laboratory examinations and
analysis carried out with integrity and technical competence will help exonerate
the innocent as well as help convict the guilty.
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