11

Chapter 15 Chapter 15 Cast and Cast and ImpressionsImpressions

Leave no trace- footprints

22

Introduction Introduction

People, vehicles, and objects leave evidence of their People, vehicles, and objects leave evidence of their presence at an accident or crime scene. presence at an accident or crime scene.

PatentPatent (not patient)impressions (not patient)impressions are two-are two-dimensional. dimensional.

Latent impressions Latent impressions are hidden to the eye. are hidden to the eye. Plastic impressions Plastic impressions are three-dimensional.are three-dimensional.

33

Shoe Impressions Shoe Impressions

The size of a shoeprint can tell the size of The size of a shoeprint can tell the size of foot of the person. foot of the person.

The depth of a foot or shoe impression can The depth of a foot or shoe impression can tell something of the person’s weight. tell something of the person’s weight.

The type of shoe can tell something of the The type of shoe can tell something of the person’s job or personality. person’s job or personality.

Databases contain the names of specific Databases contain the names of specific manufactures and tread patterns used to manufactures and tread patterns used to identify different types of shoes. identify different types of shoes.

44

Shoe Wear PatternsShoe Wear Patterns

Some factors that personalize a Some factors that personalize a person’s footwear include: person’s footwear include: Body weight. Body weight. The way a person walks. The way a person walks. The surface on which the person The surface on which the person

usually walks. usually walks. Debris that became embedded in the Debris that became embedded in the

tread or unique holes and cuts in the tread or unique holes and cuts in the tread. tread.

55

CollectionCollection of Shoe of Shoe Impression EvidenceImpression Evidence

Why would the following steps be Why would the following steps be important? important?

1.1. Take photos as soon as possible. Take photos as soon as possible.

2.2. Take multiple photos of the impression Take multiple photos of the impression from at least two different orientations. from at least two different orientations.

3.3. Place an identifying label and a ruler in Place an identifying label and a ruler in position with the impression for the position with the impression for the photo. photo.

4.4. Use oblique lighting when possible. Use oblique lighting when possible.

66

Lifting Latent ImpressionsLifting Latent Impressions

Different methods to make latent prints Different methods to make latent prints visible include: visible include: Luminol will make bloody footprints visible. Luminol will make bloody footprints visible. Dusting the latent print reveals an Dusting the latent print reveals an

impression. impression. Electrostatic lifting and gel lifting (impression Electrostatic lifting and gel lifting (impression

shown above) techniques also can capture shown above) techniques also can capture hidden impressionshidden impressions. .

77

Electrostatic Dusting Electrostatic Dusting and Liftingand Lifting

Electrostatic dusting can reveal dust left with Electrostatic dusting can reveal dust left with each step and create an impression. each step and create an impression.

Electrostatic charges can lift impressions Electrostatic charges can lift impressions from paper, carpeting, wood surfaces, from paper, carpeting, wood surfaces, linoleum, asphalt, and concrete. linoleum, asphalt, and concrete.

Other methods to recover latent impressions Other methods to recover latent impressions include gel lifters. include gel lifters.

These methods can provide information These methods can provide information about the person who left the shoe print. about the person who left the shoe print.

88

Tire Treads and ImpressionsTire Treads and Impressions

To channel water away and provide To channel water away and provide traction, a tire’s tread is divided into ridges traction, a tire’s tread is divided into ridges and grooves. and grooves.

Tires can leave patent, latent, or plastic Tires can leave patent, latent, or plastic tread patterns. tread patterns.

Tire evidence usually indicates the type of Tire evidence usually indicates the type of vehicle that left the mark, may be used to vehicle that left the mark, may be used to link a suspect or victim to a crime scene, link a suspect or victim to a crime scene, and can reveal the events that took placeand can reveal the events that took place. .

Amanda knox- bloody footprint

Casting footwear impressions

Electrostatic lifting

99

1010

Recording Tread Recording Tread ImpressionsImpressions

Ridges and grooves of discovered tire Ridges and grooves of discovered tire impressions are counted across the entire impressions are counted across the entire width. width.

Unique characteristics such as wear or pebbles Unique characteristics such as wear or pebbles embedded in the grooves are noted. embedded in the grooves are noted.

A print of a suspect’s tire impressions (through A print of a suspect’s tire impressions (through one revolution) is taken. one revolution) is taken.

Comparison with impressions from the crime Comparison with impressions from the crime scene, then, can be made. scene, then, can be made.

1111

Identifying a VehicleIdentifying a Vehicle

Identifying tread patterns may not be Identifying tread patterns may not be enough to link a suspect with a crime enough to link a suspect with a crime scene. Other things can help with this: scene. Other things can help with this: Front and rear track widths. Front and rear track widths. Wheelbase measurement. Wheelbase measurement. Turning diameter. Turning diameter.

Databases can be checked to find the Databases can be checked to find the vehicle with these specifications. vehicle with these specifications.

1212

Accident Accident ReconstructionReconstruction

Drivers may not recall the exact series of Drivers may not recall the exact series of events before, during, and after an accident. events before, during, and after an accident.

People, vehicles, and objects, however, can People, vehicles, and objects, however, can leave evidence of their actions at the scene of leave evidence of their actions at the scene of an accident. an accident.

Debris patterns and tire marks, for example, Debris patterns and tire marks, for example, can be clues to speed, direction, and vehicle can be clues to speed, direction, and vehicle identificationidentification..

1313

Accident ReconstructionAccident Reconstruction

There are three basic types of tire marks: There are three basic types of tire marks: Skid marksSkid marks—can be clues to the —can be clues to the

distance when brakes were applied and distance when brakes were applied and the vehicle’s speed. the vehicle’s speed.

Yaw marksYaw marks—can show a sideways skid. —can show a sideways skid. Tire scrubTire scrub—can determine the area of —can determine the area of

impact. impact.

How are each of these formed? How are each of these formed?

1414

Dental ImpressionsDental Impressions(movie)

Occasionally a perpetrator will leave behind a Occasionally a perpetrator will leave behind a bite mark. bite mark.

Differences in the size of teeth and jaws, Differences in the size of teeth and jaws, position, fillings, crowns, caps, breakage, and position, fillings, crowns, caps, breakage, and crowding make bite marks individual evidence. crowding make bite marks individual evidence.

1515

Dental Patterns in Dental Patterns in ForensicsForensics

The investigation consists of recognizing, The investigation consists of recognizing, docu-menting, collecting, and analyzing docu-menting, collecting, and analyzing evidence. evidence.

Up to 76 points of comparison can be used Up to 76 points of comparison can be used when comparing a suspect’s dental patterns when comparing a suspect’s dental patterns with bite marks left at a crime scene. with bite marks left at a crime scene.

Use casting as a method of comparisonUse casting as a method of comparison

1616

Crime scene

Test print Overlay

Suspect shoe

1717

Snow print wax

1818

1919

Ted Bundy

Wax Exemplar

Overlay

2020

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SummarySummary (saferstein)(saferstein)

Real CSI-Front line- 21 min inReal CSI-Front line- 21 min in Impression evidence—whether patent, latent, Impression evidence—whether patent, latent,

or plastic—will be considered class evidence or plastic—will be considered class evidence unless it has individualizing features. unless it has individualizing features.

Debris patterns and tire marks can be clues to Debris patterns and tire marks can be clues to speed, direction, and vehicle identification. speed, direction, and vehicle identification.

Differences in dental patterns can connect a Differences in dental patterns can connect a person to a crime scene. person to a crime scene.

Documentation (including photos early on) is Documentation (including photos early on) is extremely important in an investigation. extremely important in an investigation.