Making Good Impressions

Impression Evidence Imprints Indentations Striations There are three different types of impression evidence: Imprints Indentations Striations

Imprints Imprints are made when material from one area is transferred to another. Imprints are two dimensional….(l x w)

Indentations Indentations are made when the object pushes into material which is softer than the object itself. This creates a three-dimensional print... (l x w x d)

Striations Striations are related to indented impressions in that the impression leaves a three-dimensional image. There is one element that is added; the object is in motion. For example, a crowbar prying a vending machine open will not only leave a tool mark but will also leave the streaks of motion indented as well. Striations really tell a story.

Shoeprints, Tires and Tools

What can footprints tell you? Watch Where You Step! What can footprints tell you? Your range of height Your walking style Whether you are standing or running Points of entrance/exit into and out of a crime scene The path to the weapon Linkage

The Three Basic Shoeprints… Patent – tracking through a substance like paint or blood Plastic – walking through mud or snow indenting the shoeprint along the way Latent – transferring thin layers of accumulated grime to a hard surface, piece of paper, wooden floors, etc…. Invisible to the naked eye Sound Familiar?

Class vs. Individual Characteristics Shoeprints are often considered class evidence because they identify only the manufacturer and size of the shoe narrowing the search for a suspect but not pinpointing the individual.

How do you make your shoes ‘your own’? Wear patterns Cuts Nicks Scratches Gouges Stones You know… shoe stuff

What else can we learn about you? Gait patterns Walking style Length of stride Stance Pigeon-toed Slew-footed Limp Height

To cast or To mold, that is the question Cast – A reproduction of an object that made an impression… a positive replica Mold – A reproduction of the impression made by an object… a negative replica

Casting a Footprint Spray a footprint/ shoeprint with a fixative Mix up water and dental stone (or plaster if it is easier) in a gallon Ziplock bag Gently pour the plaster on a stick to ease the plaster on to the indentation.

Casting a Footprint Let the plaster set for about 25-30 minutes Etch your initials, case number, and date into the outer sole You may be able to take your cast out of the substrate at this point Let set completely for 24 hours You will get more detailed information in lab but this is the basic idea.