Introduction

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

2. Types of Impression Evidence Forensic Science: Fundamentals & Investigations, Chapter 15

3. Shoe Impressions • The size of a shoeprint can tell the size of foot of the person. • The depth of a foot or shoe impression can tell something of the 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 patterns used to identify different types of shoes. Forensic Science: Fundamentals & Investigations, Chapter 15

4. Shoe Wear Patterns Some factors that personalize a person’s footwear include: • Body weight. • The way a person walks. • The surface on which the person usually walks. • Debris that became embedded in the tread or unique holes and cuts in the tread. Forensic Science: Fundamentals & Investigations, Chapter 15

5. Forensic Science: Fundamentals & Investigations, Chapter 15

6. Collection of Shoe Impression Evidence • Photograph footprint • Photograph footprint with ruler or measuring tool for court testimony • Three dimensional footprints are casted: using material that fills impressions and then hardens to capture impression image. Forensic Science: Fundamentals & Investigations, Chapter 15

7. Tire Treads and Impressions • To channel water away and provide traction, a tire’s tread is divided into ridges and grooves. • Tires can leave patent, latent, or plastic tread patterns. • Tire evidence usually indicates the type of vehicle that left the mark, may be used to link a suspect or victim to a crime scene, and can reveal the events that took place. Forensic Science: Fundamentals & Investigations, Chapter 15

8. Recording Tread Impressions • Ridges and grooves of discovered tire impressions are counted across the entire width. • Unique characteristics such as wear or pebbles embedded in the grooves are noted. • A print of a suspect’s tire impressions (through one revolution) is taken. • Comparison with impressions from the crime scene, then, can be made. Forensic Science: Fundamentals & Investigations, Chapter 15

9. Identifying a Vehicle • Identifying tread patterns may not be enough to link a suspect with a crime scene. Other things can help with this: • Front and rear track widths. • Wheelbase measurement. • Turning diameter. • Databases can be checked to find the vehicle with these specifications. Forensic Science: Fundamentals & Investigations, Chapter 15

10. Accident Reconstruction • 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, for example, can be clues to speed, direction, and vehicle identification. Forensic Science: Fundamentals & Investigations, Chapter 15