JS 113 Forensic ScienceSlides by Jeremiah Garrido

SCCCL

Laboratory II Footwear impression laboratory

Forensic Significance of Footwear Impressions

Whether on hard or soft surfaces, the direct physical contact between the shoe and the substrate (surface) results in a transfer of class and individual characteristics from the shoe to the impression it leaves Two-Dimensional ImpressionThree-Dimensional impression

Two-Dimensional Impressions

As people walk about different they can acquire dust, dirt, residues, grease, oil, blood, and moisture onto shoes

The shoes then deposit these materials back onto other surfaces they subsequently track over

Three-Dimensional Impressions

Walking over surfaces such as sand, soil, or snow, they may cause permanent deformation of that surface

Class and Individual Characteristics

Class and individual characteristics are examined to determine if a specific item of footwear made the questioned crime scene impression, or if that item can be eliminated.

Detection and Recovery of Footwear Impressions

The primary consideration for collection of impressions is for preservation and its reproduction for later examination by the crime labBefore any impression is moved or handled it must be _______________ with a scaleSeveral shots should be taken over the impression with use of a Tripod and at different angles around impression with appropriate side lighting

Detection and Recovery of 2-Dimensional Footwear

Impressions Electrostatic Lifting-utilizes high-voltage power

source to create a static electrical charge that allows the transfer of a dust impression from the surface to a special black lifting film (mylar)

Adhesive or Gelatin Lifting- the impression may be enhanced with fingerprint powder and lifted with a gelatin or adhesive lift.

You will be performing adhesive test lifts on the three boots that may have been involved in the crime and comparing them, as footwear examiners, to a three-dimensional impression from the crime scene.

Detection and Recovery of 2-Dimensional Footwear

ImpressionsPrints in blood Chemical

enhancement Can still obtain DNA

results LCV-Leucocrystal

Violet Amido Black

Faint & Diluted Bloodstain

Detection and Recovery of 3-Dimensional Footwear

Impressionso All three-dimensional

impressions should be cast with dental stone. Dental stone is like plaster but sets much harder and has a higher compressive strength.

o Snow?

What About Impressions in Snow ?

Application of Snow Print Wax Casting with dental stone

Inscribe case info & initialsCollect & submit Cast to lab

Investigative Info Information Footwear Impressions may

provide (see lab handout)Identification of Footwear- class and individual characteristicsElimination of Footwear- Participation in the Crime-Location of ImpressionRebuttal or Confirmation of Suspects Alibis-Determination of Shoe Brand-Linking scenes of Crime-Shoe Size-Association with other evidence-Gait Characteristics-Tracking-

Lab Exercise: CRIME SCENE

During a heavy rainstorm in a large city in the Northeast, a convenience store owner was robbed and murdered in a similar manner to several prior robbery-homicides. The assailant quickly entered the store, pointed the gun at the victim’s head and shot him. The assailant then jumped over the counter and emptied the cash register. As the assailant left the store, police pursued him on foot. The long chase, through the storm, led through buildings and parks and over flat-topped roofs. The police backtracked the prints to a city park where he had hidden momentarily. In this covered area they found the gun. Next to the gun were several shoeprints of the same design. All of the shoeprints were photographed. Three individuals that fit the description of the suspect were brought in for questioning. Police observed that ALL three individuals were wearing the same brand shoe, which appears to have possibly deposited the shoeprints at the scene. Therefore, the shoes from these individuals were submitted to the crime lab for examination.

Objective 1: Make a Known Test

Impression of Footwear Submitted Using paper & fingerprint powder Produce a highly detailed sample of the class and individual characteristics of the shoes. Test impression will be compared to CS 3-D impression (cast)

Objective 2: Make a Cast of One of the Impressions at the crime scene to

compare to the Known Test Impressions taken in

Objective One

After completing your objectives, using

individual characteristics, identify which shoe

submitted to the laboratory deposited the impression at the crime

scene