Even though there are 7. 4 billion people
in the world today, no two people have the
same fingerprints. Even identical twins do
not have the same fingerprints, because they
form in the womb, beginning at around 10
weeks. While these fingerprints are forming,
all the details of the environment in the womb
can change how these fingerprints look. The
fingerprints of the developing fetus become
permanent at about 6 months.
In the 1930s, notorious U.S. bank robber
John Dillinger tried to obliterate his fingerprints with acid. More recently, a suspect in
the back of a police car bit off the ends of his
fingertips so that he could not be identified. In
both of these cases, the fingerprints could not
be erased. Like it or not, your fingerprints are
with you for life.
The value of fingerprints in forensic
science is based on Locard’s exchange
principle, which suggests that a person
always leaves something behind (and takes
something with him or her, too) every time
that person interacts with the environment.
Named after Edmond Locard of France, one
of the early pioneers of forensic science, this
observation forms the basis of forensic science as it is practiced today.
Wherever you go, you are almost certain to
leave something behind. It may be a strand
of hair, a fiber from your clothing, or perhaps
some skin cells. If you hug someone, or otherwise engage with a person physically, you
will leave behind even more evidence. But perhaps the most important thing you may leave
behind is your fingerprints.
By Brian Rohrig
N THE NIGHT OF SEPTEMBER 19, 1910, Mary Hiller was awakened in the
middle of the night by a noise coming from her daughter’s bedroom. She immediately
roused her husband, Clarence. On the way to check on their daughter, he ran into an
intruder on the staircase. After a struggle, the intruder shot Clarence twice and killed him. The
intruder, upon fleeing, touched the wet paint on a porch rail outside the house, leaving behind four
fingerprints. A man named Thomas Jennings was apprehended by police a short time later. His
fingerprints matched those found in the wet paint. These fingerprints would be used to convict
him of the murder.
This case was the first time fingerprint evidence was used to secure a conviction in the United States.
Today, fingerprinting is one of the major tools law enforcement uses to identify suspects. Everything
about fingerprints—from how they are formed to how they are analyzed—involves chemistry. It is safe
to say that without chemistry, forensic science as we know it would not exist.
The value of fingerprints in
forensic science is based on
Locard’s exchange principle,
which suggests that a person
always leaves something
behind (and takes something
with him or her, too) every
time that person interacts with