A Tool mark is any indentation, scrape, or abrasion formed when a tool makes contact with an object. Tool markings can be connected to tools used at a crime scene and used to assist identify the individual who used it.
The tool marks’ features are classified into two categories: class characteristics, and individual characteristics.
1. Class Characteristics: These are the characteristics generated by comparable type tools.
2. Individual Characteristics: As a result of wear and tear, a tool may acquire certain unique qualities over time.
Types of Tool Marks
- Saw Marks
- Drilled Holes
- Contact marks
When a tool is pushed against a surface without sliding motion, it creates an indentation. The mark merely retains the contour of the tool surface with its imperfections.
It is occasionally able to positively correlate a tool with an indentation left at the scene of the crime, which definitively ties the perpetrator to the crime.
Hammers, Punches, Dies, Metallic seals, stamps, Stones, bricks and other articles used to cause impact may also leave indentation marks. Sometimes, tools like knives, chisels, jimmies, crowbars, screwdrivers, and axes also leave indentations.
The sliding contact of a tool with the receiver surface causes scrapes marks. The surface is scratched in a distinctive manner based on the imperfections of the tool’s scratching surface.
Scrape marks take the appearance of lines. The breadth, depth, and inter-distance of the scratched lines vary depending on the angle of application, the force used, and the relative hardness of the surfaces.
If there is sliding motion, any instruments that cause indentations cause scrapes. Scrapes are also typically caused by the following tools:
• Cutting tools: swords. Knives, axes, shears, wire cutters, hatchets, Scissors, etc.
• Chisels, can-openers, crow bars, screw drivers.
• Pliers and wrenches used to turn nuts, bolts, and pipe fittings.
• Shovels used to dig the earth.
• Pieces of projected stone, brick, metal, or wood scratching against an object in motion when the latter slides against the former.
• Marks on a bullet, firing pin scrapes
Saw markings, including hack-saw marks, constitute a separate category. They only allow tool identification in exceptional circumstances. When the entire length is cut through, the saw or hacksaw leaves its cut surface pattern. The number of teeth per unit length is shown. If any teeth are fractured, the number, position, and form of the broken teeth may allow the saw or hack-saw to be positively identified.
Holes created by drills and bits in wood are usually difficult to identify. In the event that the hole is not completely through, the tool’s surface indentation may be seen at the bottom of the hole. Occasionally, the indentation may allow for precise identification of this indentation in relation to the tool.
Due to the tool’s scrape marks on the can, a punched hole in a metal sheet may frequently be identified in relation to the tool that caused the hole.
Contact marks are exchanged between objects that are joined together with glue, nails, or rivets. The presence of the contact marks establishes the fact that they were initially connected if they are removed, modified, or stolen.