Case Report
Application of Amido Black Mixture for the
Development of Blood-based Fingerprints
on Human Skin
Rodney Lawley
Birmingham Police Department
Birmingham, AL
Abstract: Amido black is a chemical blood reagent often used by
forensic specialists in the development of blood-based latent prints
on porous and nonporous surfaces. The effectiveness of this chemical
was recently tested on the dermal surface of a homicide victim. The
results were impressive, and further forensic study in this area appears
to be warranted.
Introduction
Forensic specialists are familiar with the chemical amido
black. It is a suggested treatment of visible prints and latent
prints that have been deposited in blood [1]. Amido black is
primarily composed of the substance napthol blue black. The
remaining ingredients will depend on the type of mixture that is
being prepared [1], but in this case, the methanol-based mixture
(2 g napthol blue black, 100 ml glacial acetic acid, and 900 ml
methanol) was used.
“Amido black is a chemical dye solution that binds to protein
molecules in blood and yields a dark blue color” [2]. This color
change darkens the bloody area to such a degree that many fine
details, such as dermal ridge impressions, can become clearly
visible.
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404 / 53 (4), 2003
As one might imagine, a chemical such as amido black is
highly useful at any crime scene involving the possibility of
evidentiary impressions in blood. Common crime scene applications include the development of bloody footwear impressions
on f looring, fabric impressions from bloodstained clothing, and
friction ridge impressions on a multitude of porous and nonporous surface types.
With the exceptional versatility of this mixture in mind, forensic investigators in Birmingham, Alabama recently considered
the use of amido black as a potential latent-developing agent for
bloody stains on the skin of a homicide victim. Although there
were some concerns that dermal saturation and skin tone would
reduce the necessary contrast in the amido dye, the investigators
decided that an attempt at this procedure was warranted.
Procedure
The victim’s body, with multiple stab wounds to the upper
torso, was discovered on the interior f loor of her home. Bloody
smears were observed on the ankles, both legs, and the wrist area
of both hands. This evidence strongly indicated the possibility of
a violent physical struggle between the victim and the attacker.
Because of these initial observations, investigators explored
the possibility of developing latent blood prints on the dermal
surface of the applicable body parts. This possibility, along with
a thorough latent search of the victim’s residence, became an
early focus of the crime scene investigation.
The body was first examined with an alternate light source
(ALS) for serological f luids, inherently f luorescent latent prints,
and other types of trace evidence that would be beneficial to
the investigation. This procedure produced no ridge detail but
did indicate the possibility of finger marks on the inner thigh
of the victim.
A decision was made to remove the body (prior to any further
latent search) to the county coroner’s office for the collection of
any available serological evidence. This transfer was necessary
because of the fragile nature of potential DNA evidence and
the biologically destructive properties that are often inherent
to many chemical-based latent search procedures. Great care
was taken during the removal of the body from the crime scene.
Journal of Forensic Identification
53 (4), 2003 \ 405
Investigators were well aware that any dermal contact could
destroy a potential case-solving latent print.
Upon conclusion of the coroner’s examination, the body
was fumed with cyanoacrylate acetate (super glue) utilizing
an oversized body bag as a makeshift fuming chamber on the
autopsy table. Although some sources [1] indicate that cyanoacrylate fuming is detrimental to the amido black processing
procedure, other sources [3] report that preprocessing with
cyanoacrylate fumes is not deleterious to amido black on most
substrates. This, coupled with established latent-search methods
that included the fuming technique, suggested fuming and then
subsequent amido black treatments as a practicable processing
sequence.
Following this short fuming procedure, investigators
conducted an immediate examination of the dermal surface
utilizing the ALS. No latent prints appeared. Investigators then
used a feather-type fingerprint brush to apply a f luorescent
powder to the skin surface. The results of this process were
also negative.
At this point in the investigation, a decision was made to
apply amido black to the bloodstained areas of the body. The
developer was lightly sprayed onto the affected area using a
common spray bottle. The mixture was sprayed just above the
target area, allowing the dye to slowly gravitate across the
surface of the bloodstain. This indirect application of the mist
prevents the impact damage that could occur if the f luid were
to be sprayed directly upon the stain.
Because of concerns about unwanted dermal saturation and
poor contrast of the amido dye with the dark complexion of
the body, amido exposure was limited to approximately thirty
seconds. This immersion application was immediately followed
with a rinse solution (10% glacial acetic acid and 90% methanol) as recommended by the Processing Guide. Again, the rinse
solution was also sprayed above the target area and allowed to
slowly gravitate across the stain.
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406 / 53 (4), 2003
Results
Utilizing the described amido black immersion, previously
undetected ridge detail was located on the inner right thigh of
the body. This detail, though not sufficient for a suspect comparison, demonstrated the promise this new application could hold
for future homicide investigations.
An additional nonridge imprint of the attacker’s finger
position was obtained on the same upper thigh area of the
deceased. Although this evidence is of little value for the identification of a suspect, it could prove to be a crucial element of
evidence when coupled with witness testimony, the statement of
a potential suspect, or other corroborating evidence.
Discussion
This attempt at developing blood-based prints on human tissue
was a success. Still, there are many factors that could preclude
the duplication of this success in similar investigations. It should
be noted that the victim in this particular case was deceased for
at least twenty-four hours prior to any attempts at developing
latent images on the skin. Additionally, the body had been stored
overnight in a refrigerated storage chamber (between 37 and
40 E F) and was then stored at room temperature for approximately two hours prior to processing. These factors alone can
greatly inf luence the plasticity and absorption ability of the
dermal tissue. Both of these characteristics can inf luence the
success rate of any latent search conducted on human skin.
Skin tone should also be considered as a pertinent factor when
planning a latent search of this nature. The dark blue color of the
amido black dye will not contrast well on skin that is of a similar
dark color. Although other blood reagent dyes were not tested in
this case, it is logical that similar results could be obtained with
available blood reagents of many different colors.
Conclusion
Amido black is a viable forensic tool in the enhancement of
blood prints on human skin tissue. It is versatile, inexpensive,
Journal of Forensic Identification
53 (4), 2003 \ 407
easily obtainable, and portable enough to take into the field for
field investigations.
Continued cautious experimentation with amido black,
as well as other latent-developing chemicals, should result
in further improvements in this growing subfield involving
the latent print processing of dermal tissue. More than ever,
forensic investigators must be aware of the various chemical
tools that are available for their use in any latent print search.
Additionally, they must have the confidence to apply these tools
when applicable circumstances are present.
For further information, please contact:
Sergeant Rodney Lawley
Forensic Unit Supervisor
Birmingham Police Department
1710 1st Avenue N.
Birmingham, AL 35203
(205) 254-6337
[email protected]
References
1.
2.
3.
Chemical Formulas and Processing Guide for Developing
Latent Prints; Federal Bureau of Investigation, US
Department of Justice, US Government Printing Office:
Washington, DC, 1994.
Warrick, P. Identification of Blood Prints on Fabric Using
Amido Black and Digital Enhancement. J. For. Ident. 2000,
50 (1), 20-32.
McCarthy, M. M.; Grieve, D. L. Preprocessing with
Cyanoacrylate Ester Fuming for Fingerprint Impressions
in Blood. J. For. Ident. 1989, 39 (1), 23-31.
Journal of Forensic Identification
408 / 53 (4), 2003