This type of evidence is created
when one object is pressed against another material such as soil with enough
force that an impression is made of the object. Although soil is used
as an example here, any material that can be manipulated with force may
contain impression evidence. Other such materials may be wet cement or
tar, wood, snow and even metal. Most only think of shoes and tires
when considering impression evidence, but tools and bullets can also cause
impressions.
Shoe
impressions can provide a great deal of information for investigators about
the offender. First, a shoe impression can allow the identification of
the type of shoe worn by the offender, although this may only be considered
class evidence if there is not any defects or wear that might allow for
individualization of the specific shoe. Individual wear patterns on a
shoe can be caused by the way a person walks or if the shoe is used in an
area such as on gravel or hot tar that causes unique defects. If a
specific shoe can be identified and linked to a suspect, this can be used to
prove that the suspect was at the crime scene. If there is a series of
crimes where shoe impressions were found, this can be used to link the cases
as being committed by the same offender. Several different shoe
impressions at a crime scene can assist in identifying more than one
offender responsible for a crime. Depending upon the condition of the
soil and when the crime scene is found, it may be possible to use shoe
impressions to estimate the size of the offender by measuring the depth of
the impression as compared to a known sample.
Tire impressions can be used to identify the type of tire on
the offender's vehicle by comparing the impression against a database of
known treads by manufacturer. Like shoes, tires provide class evidence
unless individual characteristics can be determined. Individual
characteristics can be caused by defects and uneven wear on the tire that
would identify it as a specific tire related to the crime. Causes for
defects and uneven wear on a tire can be caused by nails, gravel, past
attempts to patch the tire, and by unbalanced tires or from frequent sudden
stops that result in skidding.
Tools create marks when they come into contact with
materials with sufficient force. Wire cutters, bolt cutters,
screwdrivers, and crow bars are often used to pry open windows and doors and
will leave evidence where they came into contact with materials.
E-mail your questions or suggestions to
Bryan Nelson
Shoe
impressions can provide a great deal of information for investigators about
the offender. First, a shoe impression can allow the identification of
the type of shoe worn by the offender, although this may only be considered
class evidence if there is not any defects or wear that might allow for
individualization of the specific shoe. Individual wear patterns on a
shoe can be caused by the way a person walks or if the shoe is used in an
area such as on gravel or hot tar that causes unique defects. If a
specific shoe can be identified and linked to a suspect, this can be used to
prove that the suspect was at the crime scene. If there is a series of
crimes where shoe impressions were found, this can be used to link the cases
as being committed by the same offender. Several different shoe
impressions at a crime scene can assist in identifying more than one
offender responsible for a crime. Depending upon the condition of the
soil and when the crime scene is found, it may be possible to use shoe
impressions to estimate the size of the offender by measuring the depth of
the impression as compared to a known sample.
