Written by John Louis Larsen
THE PURPOSE OF THIS ARTICLE is to clarify practical evidence collection guidelines for the
recovery of latent fingerprint and DNA evidence in the field. It is the goal of
all of law enforcement to efficiently and effectively collect and preserve
evidence for trial. Physical evidence generates the foundation upon which an
affirmative prosecution can be generated.
First, I want
to clarify a number of misnomers pertaining to whether or not cyanoacrylate
(hereafter superglue fuming or “fuming”) destroys DNA. Supergluing does not destroy DNA. The fuming
process conducted in the laboratory in a fuming cabinet or a vacuum chamber
does not alter the DNA. According to Dr. Karl Reich of Independent Forensics of
Illinois1 the fuming process forms a thin “molecular size” shell
over the biological material. For example, latent fingerprint impressions
affixed to the object being fumed are covered by this thin molecular shell. The
beauty in locating a print smudge or smear is that this provides the crime
scene technician with an area that can be swabbed for DNA. This unearthed print
is called a “latent impression,” meaning hidden—“that is, the print many times
is not readily visible.”2 The latent impression is manufactured by the
transfer of bodily materials—such as oils from the scalp, hair, or moisture
(sweat)—collecting on the ridges of the impression.
process of items for latent impressions, both in the field and laboratory, will
not hinder the collection of DNA as long as the fingerprint powders and
applicators are free of DNA which could contaminate and skew the findings. The
shell-like structure masking the DNA can be dissolved with acetone. Laboratory
processing, breaking down, and clearing the site of the film generated by superglue
fuming should only be executed by trained laboratory technicians. The
laboratory should be informed as to what chemical treatments were applied to
the submitted items as well as the duration of the fuming process. I recommend
communicating with the laboratory before submitting items for processing.
Caution must be
taken to use sterile forensic tools that are clear of DNA. Processing tools consist
of 1) reusable magnetic wands with disposable plastic applicators, 2) DNA-clean
containers of magnetic and standard fingerprint powders, to include fluorescing
powders, 3) nitrile gloves, 4) protective coveralls, such as, MicroMax, 5) fluid-resistant
surgical masks (i.e. 3M N95 1860), 6) hair nets (hooded coveralls can provide
the same shielding), 7) face shields (for those with beards), and 8) footwear
covers. This basic list of material should be supplied to all crime scene
technicians. It is relatively inexpensive as seen by some of the examples
The items listed
below, in my opinion, will provide the user with the best results in the
collection and recovery of DNA in the field:
• Reusable magnetic wands and
disposable plastic applicators can be purchased in packages. For example, Doje's Forensic Supplies3 TEX Magnetic Applicator disposable covers (5-pack)
for $3.61. As seen in the image below, these are disposable magnetic applicators,
fiber and feather dusters, and applicators.
• Protective coveralls,
such as Lynn Peavey
Company’s MicroMax Protective Coveralls4, are generally available with a cost of
approximately $6.25 a unit.
Editor’s Note: Due to the
high demand for personal protective equipment (PPE) in the coronavirus
pandemic, pricing and availability is unpredictable.
personal protective breathing appliances are a must, not only for the safety of
the personnel processing the scene but also to provide a DNA proactive
contamination barrier. These can be the most-costly items. The purchase of
these items should be purchased in bulk through any of the bigger forensic
supply companies (just putting the word “forensic” on an item seems to double
the cost). An alternative that may lower the price would be to purchase through
a medical-supply company. It is the responsibility of the department to provide
PPE to officers and technical agents in the field under OSHA 29 CFR Part 1910.
through to the 2015, as a practitioner and police instructor, I worked under
the assumption that cyanoacrylate did destroy DNA. Law enforcement in general was
restrained by the fear that recovering a latent fingerprint meant they couldn’t
recover DNA through swabbing, and vice versa. Extreme caution was taken on most
items that were collected at the scene. Recovery of weapons is a good example.
As an FBI
Special Agent specializing in evidence recovery from 1991 into 2003, I had to
choose between latent impressions or DNA. In most violent crime scenes,
bloodstain, trace evidence, and fingerprint evidence are present. The choice
between latent fingerprints and DNA collection at the scene has been simplified
as a result of the laboratory being able to recover DNA after the superglue fuming
scene integrity, before items are recovered and collected by crime scene
technicians and law enforcement, agents need to make sure that items chosen to
be dusted, fumed for latent fingerprint impressions, and/or swabbed for DNA are
photographed in detail (orientation, midrange, and close-up). Skipping any one
of the photo steps may be a point of entry in court for the defense in cross
examination to lay a foundation of contamination issues as well as failure of
the officer to follow standard processing procedures. The contamination or
addition of DNA to an area to be swabbed can lead to an aggressive cross
examination which can weaken the prosecution's case by causing doubt in the
minds of the jurors. The addition of genetic material, as a result of
unintentional transferences, is probably the most significant factor confronting
law enforcement officers in the processing of scenes.
A case in point:
State of Wisconsin vs. Miguel A.F. Navarro (Pierce Co. Case No. 2018CF000156)
dealt with the August 6, 2018 murder of Israel
Valles-Flores at the hands of Miguel Navarro. Navarro's weapon was a circular saw.
Navarro and Flores were re-roofing a home. The scene of the crime started at
the peak of the roof on the second story and descended to an attached garage
roof on the first story. Local police and county sheriff deputies responded to
the scene. The sheriff’s department took over control of the scene, processing,
and overall investigation. On December 5, 2019, Navarro pleaded guilty to one
count of reckless homicide in Pierce County, Circuit Court.5
jargon, the case was a “slam dunk”. The homicide occurred in broad daylight in
front of two witnesses, as seen in the crime scene photographs below.
evidence was overwhelming, but it could have turned disastrous if any number of
evidentiary exhibits had been found to be contaminated or if the collection was
improperly done—especially in the area of fingerprints and DNA.
An area where
defense attorneys could have possibly attempted to sway the jury are seen in crime scene photographs, starting with the image below. In this
photograph, we observe sheriff detectives photographing and processing the
scene in their summer uniforms and mismatched footwear.
If the officers
are not wearing protective booties (covers) within a scene, the possibility of
generating misleading footwear impressions increases. If officers are not going
to wear shoe covers, they need to be wearing the same footwear, so that if
footwear impressions are recovered, they can easily be compared and eliminated.
If SWAT and first responders have been equipped with the same brand and style
of shoe, it becomes much easier to eliminate and compare recovered footwear
gowning (or PPE) should be mandatory in all violent scenes, not only to prevent
officers from contaminating the scene but, more importantly, to decrease the
chance of biohazardous material and trace evidence from being transferred to
them, their patrol vehicles, the department, and the officers’ homes.6
The department has a “responsibility for developing programs to protect workers.”
Based upon reviews of the pertinent data, OSHA 29 CFR Part 1910 states that “certain
employees face a significant health risk as the result of occupational exposure
to blood and other potentially infectious materials because they may contain
and contamination of evidence are the primary issues when officers work in an
extremely bloody scene without wearing protective clothing, face shields, eye
protection, or shoe covers. OSHA standards come in to play within violent crime-scene
environments—especially when dealing with bloodborne pathogens.8 In
such a case, the department could be placing officers in an unsafe position where
they could be contaminated and become instruments of contamination (by
bloodborne bio-pathogens associated with the victim whose medical history is
unknown). The department could open itself to civil suit and workers’
compensation claims. The officers working such a scene who have not been
provided with personal safety equipment become carriers and may become
infected. This leaves their department vulnerable to civil suit.
The officer processing
the rooftop murder scene wore the same evidence gloves throughout the
processing of this incident. The likelihood of cross-contamination increased the
longer they were in this scene without the proper safety barriers to shield
them and the evidence they were attempting to recover. The more they processed
the scene with only the one protective glove layer, the more items within the
scene were cross-contaminated. The officers could have unintentionally transferred
trace and biological evidence by collecting and packaging evidence while
wearing the same gloves throughout the processing of the scene.
The outside of
the packaged item(s) now become a carrier of bio and trace evidence. The
item(s) can be compared to a ticking time bomb. Contaminates are invisible, and
their very nature is transitory. Each person handling and transporting the
contaminated item becomes a potential carrier (indirect transfer) of trace and
bio evidence. This is especially true of the evidence custodian who will, in
his normal course of business, be in direct contact with the packaged evidence.
The image below is taken
from several crime scene photographs.
There are three
potential modes of contamination:
About the AuthorJohn Louis Larsen served as
a Special Agent with the FBI for 22 years and was one the founders of the FBI's
Evidence Response Team (ERT) program. His last duty assignment was with the
FBI'S Chicago Division as Senior ERT Leader. Larsen currently is President of
Larsen Forensics & Associates. He has worked as an Investigator for the
Special Prosecutors Office of Cook County and was a Senior Forensics Consultant
with Quest Consultants International, Ltd.; a sworn officer with the Office of
the Special Prosecutor of Cook Count (Illinois); and a training instructor for
Sirchie Laboratories in use of the Reflective Ultraviolet Imaging System
(RUVIS). He is also an adjunct instructor for the Homeland Security Training
Institute at the Suburban Law Enforcement Academy / College of DuPage. He is
also a contributing author to Sanford Weiss' forthcoming book, Forensic
Photography for the Preservation of Evidence from CRC Press. He can be reach at
Larsen@LarsenForensicsInc.com and at 630-418-0031.
Karl Reich, Ph.D., Chief Scientific Officer, Independent Forensics of Illinois,
500 Waters Edge, Suite 210, Lombard, Illinois 60148.
The Science of Fingerprints, FBI, United States Department of Justice, Revised
11-79), Chapter 13, Latent Impressions, page 175.
Article by Chris Gray entitled Roofer Pleads Guilty in Wisconsin Rooftop
Homicide Case, December 10, 2019, www.roofingcontractor.com/articles/94092-roofer.
Safety for the Forensic Identification Specialist 2nd Edition by
Nancy E. Masters, Master Consultations, Lightning Powder Company, Inc., 13386
International Parkway, Jacksonville, Florida 32218, Chapter 5, Biological
Hazards, Section – Universal Hazards, pages 43-44.
Ibid, Chapter 5, Biological Hazards, Section – Universal Hazards, pages 43-44.
Ibid, Employer Responsibilities, pg. 45.