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THE VALUE OF
NEGATIVE TESTIMONY
By Andrew J. Mcintyre, Fingerprint
Specialist,
Bureau of Alcohol, Tobacco &
Firearms, Forensic Science Laboratory, Atlanta, GA
Darrell R. Klasey, Fingerprint Specialist,
Bureau of Alcohol, Tobacco &
Firearms, Forensic Science Laboratory, San
Francisco, CA
One of the most rewarding aspects in the career of a
latent print examiner is the presentation of court
testimony regarding a latent print identification.
This testimony represents the culmination of the
efforts of crime scene personnel, detectives and
laboratory examiners assigned to the investigation.
In many instances, latent
prints that are recovered from evidence either do
not belong to the suspects or are not of value for
identification. Testimony regarding negative results
can be extremely useful during a trial. This paper
will discuss factors affecting latent print
recovery, the value of this type of testimony, and
how to effectively present testimony for negative
results.
Present on the palmer surface of the hands and
fingers and also on the soles and toes of the feet
is a special type of skin called friction ridge
skin. This skin has raised ridges that generally
flow from one side of the hand or finger to the
other side. As they flow across the hands and
fingers, friction ridges have certain unique
characteristics to them. Some split into two or
three separate ridges, some end part way across the
hand and others appear as dots. Friction ridges
contain numerous sweat pores, which constantly exude
perspiration. The perspiration covers the surface of
the ridges so that when a hand or finger comes into
contact with an object, an outline of the friction
ridges is deposited.
Perspiration is approximately
99% water hence it is transparent on the surface.
The term latent print is used because latent means
hidden or difficult to see. To make a latent print
visible, different techniques are used to include
chemical, powders and specialized high intensity
light. Once the latent print is made visible, it is
photographed and in the case of a powdered print,
lifted from the surface and placed on a latent lift
card. Porous surfaces, which readily absorb water,
include paper products and cardboard. Latent prints
that are
deposited on these types of items may be absorbed
into the paper fibers, thus preserving them. Latent
prints on porous surfaces have been developed on
items in excess of 40 years of age.1
Non-porous surfaces do not
readily absorb water. These items include various
types of metals, plastics and glass. When a latent
print is left on a non-porous object, it sits on the
top of the surface, thus making the print extremely
fragile as the slightest brush can destroy it's
value for identification. "Failure to recover latent
fingerprints does not in itself necessarily mean
that the prints were wiped off. The absence of
latent fingerprints on an evidentiary item may be
due to numerous factors, each depending on
conditions existing before, during, and after the
finger touched or handled the surface examined."
2
An identifiable latent print
can be defined as a set of friction ridges with
sufficient detail and clarity to be positively
identified to an individual. In order to
successfully develop an identifiable latent print,
four basic factors must occur: sweat, surface,
contact and environment.3 There must be
sufficient sweat on an individual's fingers to leave
an adequate latent print. If there is too much
sweat, the latent print will more likely be smudged.
If there is not enough sweat, the examiner may not
be able to develop the print.
Different individuals perspire
at different volumes at various times of the day. If
a person is engaged in strenuous work or is
experiencing stress due to a risky task being
performed such as the commission of a criminal act,
perspiration usually emanates at a greater rate than
when the person is at rest.4 The weather
can also play a role in the sweat factor because
when the temperature becomes colder, "the sweat
pores that exude perspiration tend to close." 5
The surface is also a main
factor in latent print development. The best surface
for a latent print to be deposited on is a smooth,
clean, flat surface. A surface that is textured,
grooved, or dirty makes identifiable latent print
recovery most difficult. Friction ridge continuity
can also be affected by the surface to the object
being handled. If a person is handling a crumpled
piece of paper or plastic, the friction ridges that
come in contact with the item will be continuous
only if the particular item stays in the crumpled
state. In most cases though, once pressure is
relieved on the item, the paper or plastic will
begin to spread out, resulting in a loss of friction
ridge continuity.6
Once there is an adequate
surface and a sufficient amount of sweat on the
fingers, there must be good contact between the
finger and the surface. If the finger grazes the
surface or is not in contact with the surface long
enough to deposit the perspiration, an identifiable
latent print probably will not be deposited. Another
problem caused by improper contact is pressure
distortion. This problem is not as critical with
porous surfaces as it is with non-porous surfaces.
In the case of non-porous surfaces, if too much
pressure is applied to the surface, the ridges may
be smudged or distorted to the point where the
examiner will not be able to use them for
identification.
Probably the most important
factor is the environment. Assuming that the first
three factors have taken place, the environmental
factor encompasses everything that happens to the
latent print from the time it is deposited to the
time that it is developed and preserved.
"Temperature, humidity, and handling are the three
primary factors within this group which may
adversely affect a latent fingerprint." 7
Since latent fingerprints are 99% water, as soon as
the fingerprint is deposited evaporation occurs. The
rate of evaporation is directly proportional to the
temperature and humidity conditions surrounding the
latent print.
Regardless of whether a latent
print identification was made or if no latent prints
of value were recovered, a pretrial conference with
the prosecuting attorney is essential. Without one,
the prosecutor will proceed with the trial based
solely on what is written in the laboratory report
of examination. Usually in the case of a negative
report, all the attorney will have to work with is a
phrase slating that no latent prints of value were
developed. Obviously, this is not sufficient to
explain how the items were processed and more
importantly, why no latent prints were found. The
prosecutor must understand that the expert's
testimony presents a more complete picture of the
overall examination.
Often a defense attorney will
try to use the defense that the defendant is
innocent because his or her fingerprints were not
developed on the evidence. The defense relies on the
jury's preconceived notions regarding fingerprints
that they have formulated by viewing entertainment
media. The majority of jurors are usually under the
impression that a person will leave an identifiable
fingerprint on anything that he or she has touched.
It is the responsibility of the prosecutor and the
examiner to educate the jury on what is fact and
what is fiction regarding the science of
fingerprints. There are times when the defense will
call the examiner to testify to his or her negative
results. The testimony given should be the same as
if the prosecutor had requested the testimony. Since
the examiner is usually employed by a governmental
entity, should a pretrial conference be scheduled
with the defense attorney, the prosecutor should be
notified of the request. In most instances, the
prosecutor will wish to attend the pretrial
conference.
By giving the jury an accurate
understanding of latent print recovery, whether or
not the testimony is requested from the prosecution
or the defense, the examiner will be able to
maintain an unbiased position. It is important, to
remember that the examiner is on the witness stand
to discuss how the examination was accomplished and
what the results of the examination were. The guilt
or innocence of the defendant is to be determined by
the judge or jury. The results of the fingerprint
examination are only to assist them in understanding
the facts of the case.
In the Oklahoma City Bombing
trial, "a prosecution expert testified that the
fingerprints couldn't be found on several pieces of
evidence to tie McVeigh to the blast that destroyed
the Alfred P. Murrah Federal Building." 8
The FBI went so far as to rip the counter out of
Elliott's Body Shop where a witness had seen McVeigh
picking up the truck two days before the bombing.
"The counter was transported to the FBI laboratory
for analysis but the examiner was unable to find
McVeigh's fingerprints. They also processed
"co-defendant Terry Nichols' pickup truck, which
prosecutors said Nichols drove to get McVeigh in
Oklahoma City after McVeigh allegedly stashed a
getaway car there three days before the blast,"
without success.
Under redirect testimony by the
prosecution, the fingerprint expert insisted that
someone could touch something and still not leave
prints. "It's very common," he added. The
fingerprint expert's job is to educate the jury as
to the facts pertaining to the development of
identifiable latent prints. Latent fingerprints are
chance impressions. The examiner should not
specifically tell the jury that the defendant is not
innocent solely because his or her fingerprints were
not developed on a particular evidentiary
item. If the expert sufficiently testifies to the
four factors listed above with a clear definition of
what a latent print is, the jury should be able to
make the connection themselves.
References:
1)
Midkiff, Charles R., "Lifetime of a Latent
Print How Long? Can You Tell?", Journal of Forensic
Identification. Vol.43No.4 July/August 1994, p.390.
2)
Olsen, Robert D., Scott's Fingerprint
Mechanics. Charles C. Thomas, Springfield, IL.,
1978, pll7.
3)
Wertheim, Pat A., International Association
For Identification Advanced Ridgeologv Comparison
Technique, unpublished, 1996.
4)
Moenssens, Andre A., Fingerprint Techniques.
Chilton Book Co., Radnor, PA, 1971, pl30-131.
5)
Alien, Sharon, "Separating Fact From
Fiction", Law Enforcement Technology. January 1992,
p24-25.
6)
Bib.
7)
Olsen, Robert D., Scott's Fingerprint
Mechanics. Charles C. Thomas, Springfield, IL.,
1978, pl21.
8)
Johnson, Kevin, "McVeigh's prints not on
evidence, expert testifies", USA Today. May 16,
1997, p4A.
9)
Ibid.
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