steps in blood, oil, or another substance. Footprints can
also be left in dust. Many footprints are pressed into
mud, snow, or other soft surfaces. Like fingerprints,
footprints are carefully photographed. Latent footprints
can be found and preserved in much the same way as
latent fingerprints. Footwear impressions (and other
impressions, such as tire tracks) are valuable pieces of
evidence, as they are three-dimensional. Investigators
often make
casts
of foot impressions. To do this, they
pour a plaster-like substance called dental stone into the
impression. When the dental stone hardens, they have a
model of the sole of the shoe. Footwear marks can help
identify the brand of shoe a suspect wears. Wear marks
on the sole can be matched to wear marks on the suspect’s
shoe. A scuff on the left heel, for example, can help set a
suspect’s shoe apart from other shoes of the same style.
Theodore Kaczynski, a serial killer also known as
the Unabomber, added smaller soles to his shoes. He wanted to
prevent people from identifying him based on his footprints.
OPPOSITE
37
AT THE SCENE
