By Ivan Ross Futrell
Mr. Futrell is a supervisory fingerprint specialist in the Latent Fingerprint
Section of the FBI Laboratory in Washington, D.C.
This Article Originally Appeared in the FBI Law Enforcement Bulletin, April 1996.
(Recent research proves that identifiable prints can be obtained from the
skin of homicide victims under real field conditions, not just in the
laboratory.)
Whether to stop them from fleeing, immobilize them, or dispose of them, murderers
often grab their victims. What homicide detective has not wished for the
ability to develop identifiable fingerprints of a suspect from the skin of
a dead body? Crucial fingerprint evidence linking the perpetrator to the
victim must be right there, but, until recently, attempts to retrieve those
prints rarely met with success.
Skin possesses a number of unique qualities that distinguish it from other
specimens examined for latent prints. Skin tissue grows and constantly renews
itself, shedding old cells that might contain the imprint of an assailant’s
grip. Its pliability allows movement and, hence, possible distortion of
fingerprints. As the skin regulates the body’s temperature and excretes waste
matter through perspiration, latent prints can be washed away.
In addition to these natural changes, the skin of homicide victims often
is subjected to many harsh conditions, such as mutilation, bodily fluids,
the weather, and decomposition after death. Further, during crime scene
processing, many people might handle a body while removing it from the scene,
which also can destroy existing fingerprints or possibly add new ones to
the corpse’s skin.
In spite of these hurdles, research conducted by the FBI Laboratory’s Latent
Fingerprint Section–in conjunction with police and medical authorities in
Knoxville, Tennessee–proves that latent fingerprints can be lifted from
skin if only investigators are willing to try. This article outlines the
history and research that led to development of a workable method for developing
identifiable latent prints on human skin.
History
The FBI has been involved in research on methods to develop identifiable
latent prints on human skin for many years. In the early 1970s, FBI scientists
reexamined existing methods using cadavers at a major university and the
Virginia State Medical Examiner’s Office in Richmond, Virginia. Most of these
cadavers had been embalmed.
To create prints, these researchers applied a coating of baby oil and petroleum
jelly to their hands and then touched areas of skin on the cadavers. At timed
intervals, they then attempted to develop these latent prints, using primarily
the iodine/silver transfer method. This method has five steps: heating iodine
in an iodine fuming gun, directing the fumes onto the skin, laying a thin
sheet of silver on the skin, removing the silver plate and, finally, exposing
the plate to a strong light, which causes the prints to become visible.
The researchers developed identifiable prints in this fashion within a time
frame that ranged from several hours up to several days after the prints
were applied. It should be noted, however, that the researchers achieved
these results under ideal laboratory conditions. It was not surprising that
they developed latent prints composed of artificially introduced oily substances
on embalmed cadavers. Yet, those early efforts provided important background
data for subsequent research conducted in Tennessee.
In 1991, a police specialist from the Knoxville, Tennessee, Police Department
contacted the FBI Latent Fingerprint Section to inquire about the FBI’s
experience and previous research on developing latent prints on skin. His
own examination of numerous homicide victims had not produced prints with
identifiable ridge detail, even though some cadavers exhibited observable
outlines of fingers and palms. Out of these discussions arose a joint research
project involving the Knoxville Police Department, the University of Tennessee
Hospital, the Department of Anthropology at the University of Tennessee,
and the FBI.
To develop a consistent and reliable technique for developing latent prints
on skin, the researchers established a protocol significantly different from
previous efforts. They decided to use only unembalmed cadavers and to place
latent prints composed of only natural perspiration and sebaceous (oily)
material. They felt that such conditions more accurately replicated field
conditions faced by police investigators.
Research
The researchers first examined the body of a 62-year-old white female who
had been dead for 9 days. Areas of skin were sectioned into numbered squares
drawn on the body. One researcher placed latent prints on the skin by wiping
his hand across his brow or through his hair and then touching the cadaver.
The researchers then tried to develop the latent prints at timed intervals
by employing several methods, including the use of lasers, alternate light
sources, iodine/silver transfer, cyanoacrylate fuming (commonly referred
to as “glue fuming”), regular and fluorescent powders, specially formulated
powders, regular and fluorescent magnetic powders, liquid iodine, RAM, ardrox,
and thenoyl europium chelate.1
Most of these methods developed the latent prints up to approximately 1 hour
after the prints had been deposited. For additional documentation, during
the next several days, researchers tested the techniques on other cadavers,
but most methods failed to provide consistent results.