Casts Impressions Chapter 15 Types of Impressions Patent

Casts & Impressions Chapter 15

Types of Impressions • Patent impressions: visible impressions – Soil, dust, paint, blood • Latent impressions: invisible – Special dusting, electrostatic techniques, chemical developers • Plastic impressions: three-dimensional – Snow, mud, Soil, soap – Easily lost – photography is important!

Individual or Class? • Tread pattern – identify brand & size, but not a specific individual – Ex: tires or shoes • Distinguishing characteristics may be individual evidence – Unusual wear, split on a shoe sole • Dental impressions are typically individual evidence

Shoe Impressions • Can determine shoe size, job or personality (type), weight (depth of impression), brand can provide information about the buyer (finances, activities, etc. ) – Cannot determine height from shoe size! • Databases exist that contain names of specific manufacturers and tread patterns used to identify different types of shoes – Many manufacturers use the same generic sole pattern – Used as class evidence to link a suspect to the crime scene by matching footwear to an impression

Shoe Wear Patterns • Wear pattern can differentiate two of the same pair of shoes – Everyone has a characteristic way of walking/usage – If individual character is strong enough, can be individual evidence • Unique holes, cuts or debris; direction of prints/impressions (point out or in); walks on toes or heels, etc.

Gait & Tracks • Numerous prints together tell an investigator about the person’s gait, or walking habits – – Injury or limp: assymetrical gait Carrying a heavy weight Walking vs. running Help recreate events • Number of people at the crime scene • Movements of individuals at the crime scene (one room or several rooms? ) • Entrance and exit to the crime scene

Collection of Shoe Impression Evidence 1. photographing impressions 2. lifting latent impressions 3. casting plastic impressions

Photographing Impressions Must be done first Perpendicular lens to reduce distortion Multiple photos from at least two angles Identifying label and a ruler (both with and without) • Use oblique lighting • Can use a light coat of color contrast paint if it is faint • •

Lifting Latent Impressions • Shoe can leave a thin film of substances from the plastic in sole or dirt – Luminol can make bloody footprints visible and able to be photographed – Dusting of latent print (like fingerprints) to reveal an impression and make it visible to be photographed and lifted – Electrostatic lifting and gel lifting techniques to capture invisible impression

Casting Plastic Impressions • Three-dimensional impression is called a cast and may be made to preserve physical evidence • Dirt: Plaster of Paris (spray with hairspray first) • Snow: spray wax, then dental stone

The Man in the Bruno Magli Shoes • • June 13, 1994 – murder of Nicole Brown Simpson & Ronald Goldman Bloody footprints, determined to be made by size 12 Bruno Magli shoes, tracked the victims’ blood along the path Specialists determined that the impression was made about 20 minutes after the attack. OJ Simpson denied owning a pair of Bruno Maglis, and the prosecutor could find no way to dispute this fact Footprint evidence was of little value in the criminal case After criminal trial ended, photo was found showing Simpson wearing similar shoes In civil case that followed jurors believed the attacker made the footprints, and Simpson was found responsible for the deaths of Brown and Goldman