Written by Debra HolbrookCourtesy of the Academy of Forensic Nursing
A VICTIM CALLS 911 with a
domestic complaint involving assault and strangulation. Law enforcement personnel
arrive but see no visible injury to either party and no arrest is made. The
victim transports herself to a local hospital where she is discharged in stable
condition, having no neck CT as no injuries were noted.
This is a scenario that plays
out across towns and cities every day involving unwitnessed histories of
assault where no injury is seen. Variations to this complaint may include the
victim being a person of color where detection of bruising is more challenging,
or a victim whose emergent bruising is so faint that it is obliterated with a
flashlight, or unable to be seen in a photograph. But all have one thing in
common: a victim with injuries that are poorly visualized by the naked eye.
Bruising and Wounds
So, the question remains: Why
are bruises sometimes so difficult to detect?
To answer this, we must
understand the causation and properties of bruising. A bruise is caused by
blunt- or squeezing-force trauma and may also be referred to as a contusion. It
may present as firm (indurated), painful, and initially varies in color from
red to purple. Bruises are caused by capillary blood vessel rupture and
extravasation of the bleeding in the epidermal, dermal, and subdermal tissues
without the skin being broken.
Visualization of bruising
secondary to trauma is dependent on many factors including but not limited to:
victim age, amount of force used, depth of the wound, location on the body,
medications taken by the victim, as well as their physical condition and degree
of pigmentation in the skin. Even bruising that appears at the epidermal level may
be difficult to visualize on a victim with darkly pigmented skin as compared to
one who is lightly pigmented.
Small, blunt-force trauma and
ligature strangulation will generally leave visible wounds due to energy being
focused to a smaller area and the rupture of capillaries; while trauma by a
large object, including manual strangulation, will rarely leave bruising at the
epidermal level since the energy dispersed to a larger area of the body decreases
capillary rupture at the surface. This does not mean that there is not bruising
or bleeding into deeper layers of the dermis, or subcutaneous layers of the skin—it
only means that this bruising is too deep to be seen with an unaided eye. Deep
bruises may take days or weeks to come to the surface, or they may never do so.
The cycle of the bruise is as
follows: blood vessels break to release erythrocytes; erythrocytes break down
to release hemoglobin; and hemoglobin breaks down to release bilirubin. This
cycle demonstrates the body’s process of dissolving the bruise and absorbing it
as waste. During the hemoglobin-to-bilirubin phase, the red to purple bruise
may turn green to yellow in color.
But what if there was a method
of assessing a victim/patient that could aid the eye in seeing wounds beneath
the skin? What if it did not matter how darkly pigmented the victim was or how
faint the wound appeared, but gave all victims the same advantage in regard to
having their wounds documented? That method is alternate light source
Alternate Light Sources 101
An ALS is nothing more than a
powerful lamp that emits light in the forms of ultraviolet, visible, and
infrared wavelengths. The ALS filters this light into color bands, or
wavelengths, that allows one to see evidence by fluorescence (evidence glows),
absorption (evidence darkens), and oblique lighting or reflection (where small
particles of evidence are visible). When light strikes a surface or compound,
it will either be absorbed, reflected, transmitted, or a combination of all
three. The actual interaction is between the photon of light and electrons
bound to the atoms of the surface.
Where white light is composed of
a combination of wavelengths ranging from 190–700 nm, an ALS allows the
selection of specific ranges of wavelengths by filtering the rest. For
instance, a setting of 350 wavelength on most commercial units would give a
range of approximately 330–370 nm, allowing one to visualize evidence at a
Commercial ALS units come as flashlights
with one wavelength per flashlight, or as a unit where different wavelengths
may be selected (generally four to six pre-selected wavelengths). As the
wavelength increases, the amount of energy decreases—so the higher the
wavelength, the deeper the penetration of the skin. The deeper the penetration,
the better one is able to visualize latent wounds beneath the epidermis and
into the dermis and sub-cutaneous layers of the tissue.
Evidence tends to fluoresce on
the skin at lower wavelengths (190–350 nm). You may be familiar with this set
of wavelengths as a “blacklight” where substances and fibers tend to glow. Blood
does not have properties that fluoresce, so blood—even on the surface of the
skin—will appear darkened due to absorption of the wavelengths. As the
wavelength is increased, the light begins to penetrate into the dermis (300–400
nm) and even into the subcutaneous layers under the skin (400–650 nm.) (Figure
1). Infrared wavelengths are not used in victim/patient evaluation due to the
damaging effects of this light at a cellular level that is known to cause
cancer (700–900 nm).
Due to the intensity of the
light, it is essential that goggles are worn, not only for the protection of
the eye, but to further filter light and determine the best visualization of
the surface area. When using a light source and goggles to detect evidence, you
are using different wavelengths to detect fluorescence, absorption, or
reflection. Goggles are long-pass filters that block the excitation wavelength
(also known as the light we are using to see the evidence) from hitting our
eyes, allowing us to see the weak fluorescence or absorption created by the
light source. Goggles are yellow, orange, and red in color. Some manufacturers
use a mixture of these colors in their goggles, so orange may be a mixture of
yellow and orange. We use multiple wavelengths to attempt to reduce the
visualization of backgrounds so we can get a better contrast of the evidence that
we are looking for. As we go from lower to higher wavelengths, the goggles lose
their ability to block the light coming from the light source, so we need to
change goggles as we change wavelengths to make sure no light is “leaking
through” our goggles—which would cause us to either visualize less evidence or
none at all.
Because all people have
capillary rupture (bruising) at different thresholds due to injury, there is no
constant ALS wavelength that can be used to detect latent injury on every
victim. It is essential that all available wavelengths—most often 300–600 nm—be
used in combination with all goggle colors for optimal evaluation of an injury.
Tattoos, blood vessels, and areas of hyperpigmentation will also show
absorption and must never be confused with wound absorption. An ALS can be a
valuable tool in defining wounds such as bitemarks, and defining patterns
associated with mechanism of injury and central clearing.
Simplified: an ALS is a tool to
aid an investigator or practitioner in seeing that which is not apparent, much
like corrective lenses aid one in reading or a microscope aids in seeing that
which is too small to see without magnification. An ALS does not require
calibration. Maintenance is limited to changing batteries and the light bulb,
and modern units are lightweight and easy to use.
Synopsis of Research Supporting ALS in Identification of Wounds
Since the early 1990s, research
has been published linking ALS technology to the ability to identify latent
wounds on the body:
ALS in Judicial Proceedings: Maryland Challenge
The relevant standard of the Frye standard adopted by the Maryland Court
of Appeals in Reed v. State, 283, Md. 374
(1978) holds that before
expert testimony based on the “new” scientific process can be admitted into
evidence, it must first be established that the technique used is reliable.
The first argument is that ALS
is not a process or a technique. There is nothing subjective about ALS. A light
is turned on and an examiner either sees florescence or absorption… or they do
not, making ALS more of a tool than a process.
As defined earlier, ALS is not a
“new” technology and has been used in crime scene investigation and forensic
medical examinations for many years. Since the early 1990s studies have shown
that ALS can be used to identify latent injuries, including bruising—thus supporting
its “validity and reliability” and acceptance in the scientific community. Forensic
Nurses use these units on a daily basis to perform forensic medical evaluations
of victims of crime. ALS rulings have been upheld in Baltimore Circuit Courts
that use of an alternate light source has gained general acceptance and is
standard in the field of forensic nursing.
Questions used to successfully
challenge ALS motions may include:
ALS units may be brought into court for
motion trials along with goggles or filter shields. Demonstration of the unit
and how it is used on a victim/patient are particularly useful in educating the
judge and/or jury in ALS use. Generally, it is more confusing to a jury to
explain ALS than showing that it is a light that is relatively easy to use.
An alternate light source is a
powerful lamp that emits light in ultraviolet, visible, and infrared
wavelengths and goggles must be worn to fully visualize florescence, absorption,
or reflection to identify evidence.
It is essential that all wavelengths
and goggle colors be worn to adequately identify evidence or latent injury. Documentation
should include: 1) type of finding (fluorescence, absorption), 2) wavelength
under which evidence was best visualized, 3) filter color used to visualize
(goggle color), 4) topical products applied (if used on skin surface), and 5) a
detailed history that may have contributed to the wound.
ALS units are easy to use and require
no calibration. However, it is essential that staff be trained to use these
units and have an understanding of what they are seeing with the light to
assure effective documentation and potential expert court testimony.
About the Author
Debra S. Holbrook (MSN, RN,
SANE-A, SANE-P, FNE A/P, DF-AFN, FAAN) completed both undergrad and graduate studies
through Wilmington University. In 2002, she testified on Capitol Hill before a
Senate Judicial Subcommittee on Crime and Drugs on behalf of the bill that was
signed into law in 2005 as the DNA Justice Act. She is the recipient of
numerous international awards, including the ANCC Magnet International Nurse of
the Year, the Delaware Nurse of the year, the International Association of
Forensic Nurses Pioneer Award, the 2014 Most Influential Marylanders in
Healthcare, Distinguished Fellow—Academy of Forensic Nursing, and the
prestigious Fellow American Academy of Nursing. She serves on the board of the
Academy of Forensic Nursing and lectures nationally and internationally on
forensics across the lifespan. Holbrook has integrated comprehensive forensic practice
into the SANE model and her programs have cared for patients of
interpersonal violence including domestic, elder, child, institutional,
vulnerable populations, gunshots, stabbings, non-accidental poisonings, and
burns. She has pioneered the use of the alternate light source in strangulation
cases and set precedence in national court systems. She is currently Director of Forensic Nursing at Mercy Medical Center in Baltimore, where she coordinates
care to victims of interpersonal violence for all hospitals in Baltimore City.
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