Chapter 15 Cast and Impressions By the end

Chapter 15 Cast and Impressions By the end of this chapter you will be able to: o o Distinguish between patient, latent, and plastic impressions Describe how to make foot, shoe, and tire impressions Use track width and wheel base information to identify vehicles Prepare dental impressions and match them with bite marks All Rights Reserved South-Western / Cengage Learning © 2012, 2009 1 Forensic Science: Fundamentals & Investigations, Chapter 15

What is impression evidence? Impression evidence can be defined as objects or materials that have retained the characteristics of other objects through direct contact. Impressions are created when one object is pressed against another material with enough force to leave an impression of the object. Shoeprints, tool marks, tire tracks, bite marks, and marks on a fired bullet are several examples of impression evidence. Impressions may be found in or on many different types of materials. The quality of the impression depends on the object making the impression and the surface conditions, such as how hard or soft it is and what type of material it is (soil, mud, dust, concrete, grass, skin, etc. ) Images: http: //upload. wikimedia. org/wikipedia/commons/archive/6/61/20070917141644!Shoeprint(forensic). jpg and http: //www. topmark. co. nz/images/content/tmpics 01/gallery-s/Silipression. Teeth. Mold. jpg CSI & Impressions

Introduction People, vehicles, and objects leave evidence of their presence at an accident or crime scene. o o o 3 Patient impressions are two-dimensional Latent impressions are hidden to the eye Plastic impressions are three-dimensional Forensic Science: Fundamentals & Investigations, Chapter 15

Collection Methods Investigators analyze the impression evidence to find unique characteristics to link shoes, tires, tools, and other objects found in a suspect’s possession to evidence at a crime scene. Collection of impression evidence can be accomplished using several methods: 2 -D: This type of impression is documented using photography. Some impressions may be dusted with fingerprint powder to be photographed or lifted with tape. They may also be collected using an electrostatic dust lifting process. 3 -D: This type of impression can be documented using photography as well as by casting, which involves using dental stone or a similar substance to preserve the dimensional characteristics of the print. Images: http: //www. evidentcrimescene. com/cata/cast/dscasting. html

Shoe Print Evidence Investigators can analyze a shoe print to determine its class, or the type and brand of shoe. They will also look for individual characteristics, such as wear patterns and specific damages or defects. Databases of shoe prints are available for investigators to help them determine the brand of shoe to provide leads for a case. Depending on the quality of the impression, 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. Features to analyze: • Tread patterns, size, and depth • Wear patterns caused by the way a person walks • Material defects or damage (nicks, cuts, etc. ) • Other trace materials, such as soil, tar, rocks, and paint that would indicate where a person has been Images: http: //www. stampmatch. com/results. html and http: //www. fosterfreeman. com/products/shoeprints/solemate. html STAMP Database Shoe Print in Bio-Foam Impression Foam

Shoe Impressions o o 6 Shoeprint size indicates the foot size The depth of a foot or shoe impression indicates a person’s weight The type of shoe can tell something of the person’s job or personality Databases contain the names of specific manufactures and tread designs Forensic Science: Fundamentals & Investigations, Chapter 15

Shoe Wear Patterns Factors that personalize a person’s footwear: o Body weight o The way a person walks • Weight distribution • Direction of toes (straight, pointing out or in) o o 7 The surface on which the person walks Unique holes, cuts, and debris embedded in the tread Forensic Science: Fundamentals & Investigations, Chapter 15

Collection of Shoe Impression Evidence Why would the following steps be important? 1. Take photos as soon as possible 2. Take multiple photos of the impression from at least two different orientations 3. Place an identifying label and a ruler in position with the impression for the photo 4. Use oblique lighting when possible 8 Forensic Science: Fundamentals & Investigations, Chapter 15

Lifting Latent Impressions Different methods to make latent prints visible: o o o 9 Luminol makes bloody footprints visible for photography Dusting the latent print reveals an impression for lifting or photography Electrostatic lifting and gel lifting (image below) techniques can capture hidden impressions Forensic Science: Fundamentals & Investigations, Chapter 15

Electrostatic Dusting and Lifting o o o 10 Electrostatic dusting reveals dust left with each step and creates an impression Electrostatic charges can lift impressions from paper wood surfaces carpeting linoleum asphalt concrete Gel lifters also recover latent impressions Forensic Science: Fundamentals & Investigations, Chapter 15

Comparing Shoe Size and Height 11 Forensic Science: Fundamentals & Investigations, Chapter 15

Tire Track Evidence Tire tracks are important in forensic investigations and are usually found in road accident scenes or in the access and escape routes of other crime scenes. Tracks help investigators identify the type of vehicle that left them. Investigators may make ink prints of a tire or plaster casts of a track. They will also take photographs that can later be used to prove a match. Features to analyze: • Tread pattern • Width & depth of the tread pattern • Unique characteristics due to the wear pattern or defects Tire databases are available help investigators determine the brand model of the tire that left the impression , which can be used to determine the type of vehicle that made the tracks. Images: http: //www. suite 101. com/view_image. cfm/454216, http: //www. ronsmithandassociates. com/FWTTS. htm.

Tire Treads and Impressions o o 13 Tire treads—ridges and grooves channel water away and provide traction Patent tread patterns—impressions made after tire runs through a fluid material Latent tread patterns—impressions from tire oils used to keep tires soft and pliable Plastic tread patterns—three dimensional impressions left in soft surfaces Forensic Science: Fundamentals & Investigations, Chapter 15

Tire Treads and Impressions o o o 14 Tread patterns can indicate the type of vehicle that left the mark Link a suspect or victim to a crime scene Reveal events that took place at the scene Forensic Science: Fundamentals & Investigations, Chapter 15

Anatomy of a Tire 15 Forensic Science: Fundamentals & Investigations, Chapter 15

Recording Tread Impressions o o o 16 Count ridges and grooves across the tire width Note unique characteristics—wear or pebbles embedded in the grooves Create a print of the suspect’s tire impressions through one revolution Compare impressions from the crime scene and suspect’s tire Identifying tread patterns may not be enough to link a suspect with a crime scene Forensic Science: Fundamentals & Investigations, Chapter 15

Identifying a Vehicle Track widths— From center of tire to center of tire Wheelbase length— From center of front axle to center of rear axle 17 Forensic Science: Fundamentals & Investigations, Chapter 15

Identifying a Vehicle o Turning diameter Databases can be checked to find the vehicle with these specifications 18 Forensic Science: Fundamentals & Investigations, Chapter 15

Accident Reconstruction o o o 19 Drivers may not recall the exact series of events before, during, and after an accident People, vehicles, and objects, however, can leave evidence of their actions at the scene of an accident Debris patterns and tire marks can be clues to speed, direction, and vehicle identification Forensic Science: Fundamentals & Investigations, Chapter 15

Accident Reconstruction There are three basic types of tire marks: o Skid marks—clues to the distance traveled after brakes are applied and the vehicle’s speed Yaw marks—shows a sideways skid o Tire scrub—determines the area of impact o How are each of these formed? 20 Forensic Science: Fundamentals & Investigations, Chapter 15

Bite Mark Evidence Investigators can analyze bite marks for characteristics to help them identify victims or suspects as well as to exclude others. Marks can be left on a victim’s skin or other objects, such as Styrofoam cups, gum, or foods. Saliva or blood may be left behind that can be tested for DNA. Dental records including x-rays can also provide useful information, especially when attempting to identify a victim. Bite Mark Evidence Video Features to analyze: • Type of bite mark (human or animal) • Characteristics of the teeth (position, evidence of dental work, wear patterns, etc. ) • Color of area to estimate how long ago the bite occurred (old or recent bite) • 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. Images: http: //www. forensicdentistryonline. org/Forensic_pages_1/currentopic 1. htm, http: //www. trestonedental. co. uk/images/0303. jpg

Dental Impressions o o 22 Occasionally a perpetrator will leave behind a bite mark—considered individual evidence Note differences in the size of teeth and jaws, position, fillings, crowns, caps, breakage, and crowding Forensic Science: Fundamentals & Investigations, Chapter 15

Development of Teeth 23 Forensic Science: Fundamentals & Investigations, Chapter 15

Dental Patterns in Forensics o o 24 The investigation consists of recognizing, documenting, collecting, and analyzing evidence What are the two basic ways dental patterns can be used in forensic investigations? There are 76 points of comparison when comparing a suspect’s dental patterns with bite marks left at a crime scene What is the common method used to reveal whethere is a match? Forensic Science: Fundamentals & Investigations, Chapter 15

. . . . Summary o o 25 Impression evidence—whether patent, latent, or plastic—will be considered class evidence unless it has individualizing features. Debris patterns and tire marks can be clues to speed, direction, and vehicle identification. Differences in dental patterns can connect a person to a crime scene. Documentation (including early photos) is extremely important in an investigation. Forensic Science: Fundamentals & Investigations, Chapter 15