Tool Marks

Tool Mark Definition: impression left by the contact of a tool onto a surface Importance: establish a link between a tool mark and the tool that created it

Two Kinds of Characteristics Class: type of impression, its general shape and its general dimensions Help determine type of tool and how the mark was created CANNOT be used for identification of exact tool Individual: AKA accidental are the striations and small particularities exhibited by the tool that are individual or unique to one tool These characteristics provide formal identification

Two Types Slipped/Scratches: occurs as the tool drags or slides across a surface, result is series of striations Ex: keying someone's car, cutting of knife Molded/Impressions: contact of a tool onto a surface with no lateral motion (no drag or slip) which cause a 3D mold of the tool that contacted the surface Ex: breaking a door with a pry bar, serial number stamped on a gun barrel

Pictures Slipped Molded

Examination Process Step 1: Observation, measurement, and description of tool mark Step 2: Photo’s are taken Step 3: If the tool cannot be taken as is a cast is made Step 4: Comparison tool marks are made on a soft surface to not remove or change individual characteristics Step 5: Compare incriminating tool mark verses comparison mark under microscope

Evidence Examples Bolt cutters Screwdrivers and chisels Scissors Knives and box cutters Pliers and wrenches Crowbar Saws

Places to Look for Tool Marks Wire, chains Door and window frames Sections of sheet metal Safety-deposit boxes, safes Padlocks, doorknobs Bolts and locks