impression evidence - lhs science -...
Post on 01-May-2018
221 Views
Preview:
TRANSCRIPT
IMPRESSION EVIDENCE
Terminology• 2-D (two dimensional) Impressions – impressions with two
dimensions (length and width) such as impressions in dust, blood, etc. on a hard surface
• 3-D (three dimensional) Impressions – impressions with three dimensions (length, width, and depth) such as impressions in dirt or snow that have depth
• Accidental/Unique Characteristics – cuts, scratches, and other damage which can be used to individualize a shoe to an impression
• Elimination Prints – Known print
– Ex: Photos of the bottoms of the shoes of all personnel that enter the crime scene
• Latent Impression – an impression that is invisible without some type of enhancement or oblique lighting
• Partial Impression – an incomplete impression that only has a portion of the overall tread design present
Bite Marks/Teeth Impressions• Universal system - A number is assigned to
each of the thirty-two adult teeth, beginning at
#1 with the upper right third molar and ending
with the lower right third molar
• Teeth are tools and a tooth mark is like a tool
mark.
– teeth that leave the strongest impressions
are in the front, both top and bottom
– chip, get worn down, or be reshaped in
various ways
– restorations, fillings, rotations, tooth loss,
breakage, and injury that can make one
person's teeth unlike anyone else's
• Sometimes a bite-mark has to be charted and
examined from many angles; sometimes it can
be identified from one tooth
• Bite marks left on foodstuff, such as cheese or gum, offer a three-
dimensional impression, which is superior to the two-dimensional
impression often left on skin.
• A bite might penetrate the skin, but often only leaves bruising
– sometimes the blood marks of a bruise are mistaken for the
impression of a tooth.
– skin gets distorted when bitten, or the teeth slide during the act of
biting.
– Some bites are forceful enough to leave a good impression, others
are not.
The physical characteristics of both the bite mark wound and the suspect's
teeth include:
-the distance from cuspid to cuspid
-the shape of the mouth arch
-the evidence of a tooth out of alignment
-teeth width and thickness, spacing between teeth
-missing teeth
-the curves of biting edges
-unique dentistry
-wear patterns such as chips or grinding.
Case Example
• Bundy's teeth and
bite marks on Lisa
Levy
(trial evidence)
• The tissue from Lisa Levy's
buttock had been destroyed
in all the analyses, but the
photograph with the ruler
still remained.
• Pointed out how unique the
indentation mark was and
showed how it matched the
dental impressions of
Bundy's teeth.
• First case in Florida's legal
history that relied on bite-
mark testimony, and the
first time that a physical
piece of evidence actually
linked Bundy with one of his
crimes.
Shoes & Shoeprints
2-D Footwear
3-D Footwear
Accidentals
Elimination Prints
• Negative Impression – impression created by shoe treads coming into contact with a dirty surface and taking dirt/dust away (areas where the shoe made contact are clean with dirt/dust around them)
• Oblique Lighting (side lighting) – lighting at an angle with respect to the impression (usually approximately 30 to 45 degree angel for 3D impressions and 10 degrees to parallel with the floor for 2D impressions)
• Positive Impression – impression created by dirt or other residue on the shoe treads that is left behind on a surface (areas of a floor where the shoe made contact are soiled by dirt or other substance that was adhering to the bottom of the shoe)
• Tread Element – the individual treads that make up a tread design of a shoe or tire
• Wear Characteristics – As the a shoe is worn, the tread elements wear down and can change their shape or texture
Footwear Terminology
Negative Impression
Positive Impression
Tread Elements
(Footwear)
Footwear Comparison
Tread Design (class character)
Size of Tread Design (class character)
Wear Characteristics (unique)
Accidental or Unique Characteristics
(unique)
Can be as individual as a fingerprint
Must have shoes to make a positive ID
Known Impressions
Class
Characteristics:
•Tread Design
•Size of Tread
CAN’T be used to
individualize
Photo of Suspect’s Shoe
Q K
Known
Impression
Questioned
Impression
Comparison Results
• If the shoes are dissimilar in tread design, the shoe is ELIMINATED
• If the shoe has same tread design, but different size it is also ELIMINATED
• If the shoe has similar tread design and size, the shoe COULD HAVE made the impression
• If the shoe has similar tread design, size, and a couple of accidentals (but not enough for positive ID), the shoe LIKELY made the impression
• If Similar tread design, size, and enough accidentals, it is a POSITIVE ID
How Many Accidentals?
• No specific number required for positive ID
• Based on experience of the examiner, types
of accidentals present and how clear the
accidentals are in the questioned
impressions
• Accidentals have different
weights/significance depending on shape
and size
Tire Tread
• record and analyze impressions of vehicle
tire treads
• Initially can tell the brand of tire
• every tire will show different amounts of
tread wear & different amounts of damage
– tiny cuts and nicks
– defects and wear caused by nails, gravel,
patches and alignment problems
• unique characteristics will show on the
impression left by the tire.
Other Prints
• Palm - friction ridges can
be identified and may be
used against suspects
• Lips—display several
common patterns
Other Prints
• Footprints
–size of foot and toes;
friction ridges on the
foot
–Taken at birth as a
means of identification
of infants
Other Prints
Ears—shape, length and width
Voice—electronic pulses
measured on a spectrograph
Other Prints
The blood vessel
patterns in the eye
may be unique to
individuals. They are
used today for various
security purposes.
top related