I Impression Evidence A Def objects or materials

I. Impression Evidence A. Def: objects or materials that have retained the characteristics of other objects through direct contact. 1. Created when enough force leaves an impression of the object. • Ex: Shoeprints, tool marks, tire tracks, bite marks, and bullet/case marks. 2. Found on many different types of materials. 3. Quality depends on the object making the impression and the surface conditions • Ex: how hard or soft it is and what type of material it is (soil, mud, dust, concrete, grass, snow, skin, etc. ) CSI & Impressions

B. Collection Methods -several methods depending on materials 1. 2 -D Impression (visible or latent): from soil, dust, paint, blood, or other fine particles a. photograph b. dust with fingerprint powder to be photographed or lifted with tape. c. use an electrostatic dust d. use gel lifting 2. 3 -D Impression a. photograph b. cast it Example of Shoe Print in Bio -Foam Impression Foam

II. Bite Mark Evidence • Individualized Evidence • Can identify victims or suspects and/or exclude others. • Marks can be left on a victim’s skin or other objects (Ex: Styrofoam cups, gum, food) • Saliva or blood may be left behind DNA. Features to analyze: 1. Type of bite mark (human or animal) 2. Characteristics and measurements of the teeth (position, evidence of dental work, wear patterns, etc. ) 3. Color of area to estimate how long ago the bite occurred (old or recent bite) 4. Swab for body fluids for DNA tests Did you know? The most famous incident where bite mark evidence led to a conviction, was in the case of the notorious serial killer, Ted Bundy. He was responsible for an undetermined number of murders between 1973 and 1978 and was finally tied to the murder of Lisa Levy through bites that he had inflicted on her body. Bite Mark Evidence Video

WS: Bite Mark Cases CLAIM: Does each Case (#1 -3) belong to Suspect A or Suspect B? • • EVIDENCE: • • Tooth Rotation Arch Width Dental Work Wear Patterns *Mx = Maxilla (top) *Mn = Mandible (bottom) WHICH TOOTH is rotated? (in mm)

Tire Track Evidence

III. Tire Track Evidence • Can be individualized or identified • usually found in road accident scenes or in the access and escape routes of other crime scenes. • Investigators may make ink prints of a tire or plaster casts of a track. • photographs can later be used to prove a match. • Tire databases help determine the brand model of the tire – Can be used to determine the vehicle type Features to analyze: 1. Tread pattern 2. Width & depth of the tread pattern 3. Unique characteristics due to the wear pattern or defects My Cousin Vinny

Tool Marks & Shoe Prints

IV. Tool Mark Evidence • Defects or patterns are left on a tool when it is made or used, which can be used to find matches between evidence at a crime scene and tools or objects found at a suspect’s home. Tool marks Classification: (1) Indentations – when tool is pressed into a softer surface, the shape of the tool and imperfections may be left behind. (2) Abrasion Marks – when a tool moves across a surface, may leave ridges or striations (3) Cutting Marks - produced along the edge as a surface is cut **NOTE: Some tool marks are a combination Features to analyze: • Dimensions of the impression • Ridges or striation patterns • Defects, such as nicks and chips • Paint chips or metal shards left on a tool

Using comparison microscope

V. Shoe Print Evidence A. Investigators will: 1. Photograph 2. Make a cast mold or dust print 3. determine class (type and brand) • Databases of shoe prints available B. Impression Quality? • STAMP Database investigators may be able to determine a person’s speed (walking vs. running) as well as estimate the size of a person based on the impression’s depth. C. Features to analyze: 1. Tread patterns, size, and depth 2. Wear patterns caused by the way a person walks 3. Material defects or damage (nicks, cuts, etc. ) 4. Other trace materials, such as soil, tar, rocks, and paint that would indicate where a person has been Shoe Print in Bio-Foam Impression Foam