Skid mark
Encyclopedia
Trace evidence
Trace evidence is evidence that occurs when different objects contact one another. Such materials are often transferred by heat induced by contact friction....
analysis in forensic science and forensic engineering
Forensic engineering
Forensic engineering is the investigation of materials, products, structures or components that fail or do not operate or function as intended, causing personal injury or damage to property. The consequences of failure are dealt with by the law of product liability. The field also deals with...
. Skid marks are important for finding the maximum and minimum vehicle speed prior to the impact or incident. Skidding can also occur on black ice
Black ice
Black ice, sometimes called glare ice or clear ice, refers to a thin coating of glazed ice on a surface.While not truly black, it is virtually transparent, allowing black asphalt/macadam roadways to be seen through it, hence the term "black ice"...
or diesel deposits on the road and may not leave a mark at all.
Skid marks are divided into "acceleration marks" created on acceleration, if the engine provides more power than the tire can transmit; "braking marks," if the brakes "lock up" and cause the tire to slide; or "yaw
Yaw
The word yaw can refer to:* Yaw angle, one of the Tait-Bryan angles, describing the heading of a vehicle or machine, and some other related elements:**Yaw system, component responsible for the orientation of a wind turbine towards the wind....
marks", if the tire slides sideways. Each has a characteristic appearance, and an experienced accident reconstructor or forensic engineer can often determine what the vehicle was doing by examining the marks left by the tire.
In car accidents, skid marks are caused by rubber being deposited on the road, much like that of an eraser
Eraser
An eraser or rubber is an article of stationery that is used for rubbing out pencil markings. Erasers have a rubbery consistency and are often white or pink, although modern materials allow them to be made in any color. Many pencils are equipped with an eraser on one end...
leaving pieces of rubber
Rubber
Natural rubber, also called India rubber or caoutchouc, is an elastomer that was originally derived from latex, a milky colloid produced by some plants. The plants would be ‘tapped’, that is, an incision made into the bark of the tree and the sticky, milk colored latex sap collected and refined...
on a paper. Skid marks can also come about when a car suddenly accelerates on a slippery surface, or takes a hard corner. Skid marks are not made by temporary melting of the road surface, as can be shown by skid marks made on concrete by a bicycle, with children often having competitions about who can create the longest skid mark. The rubber of car tires heats up with sliding friction, degrades and disintegrates at the road-tire interface, and is deposited on the road surface.
Accident reconstruction
Vehicular accident reconstruction
Vehicular accident reconstruction is the scientific process of investigating, analyzing, and drawing conclusions about the causes and events during a vehicle collision...
, when their size and shape can reveal much about vehicle speed and forces of acceleration or deceleration. They are one form of trace evidence
Trace evidence
Trace evidence is evidence that occurs when different objects contact one another. Such materials are often transferred by heat induced by contact friction....
. They represent a form of contact evidence produced according to Locard's exchange principle
Locard's exchange principle
The Locard exchange principle, also known as Locard's theory, was postulated by 20th century forensic scientist Edmond Locard.Locard was the director of the very first crime laboratory in existence, located in Lyon, France...
. The length of the skid mark is usually closely related to the vehicle speed at the instant of braking, so measuring the marks yields an estimate of original speed.
Skid marks can also be formed where a ladder
Ladder
A ladder is a vertical or inclined set of rungs or steps. There are two types: rigid ladders that can be leaned against a vertical surface such as a wall, and rope ladders that are hung from the top. The vertical members of a rigid ladder are called stringers or stiles . Rigid ladders are usually...
suddenly slips and the user falls to the ground, especially if the ladder feet are faulty or absent. Loss of the rubber
Rubber
Natural rubber, also called India rubber or caoutchouc, is an elastomer that was originally derived from latex, a milky colloid produced by some plants. The plants would be ‘tapped’, that is, an incision made into the bark of the tree and the sticky, milk colored latex sap collected and refined...
feet or foot causes the aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
stile to make contact with the ground, and if a hard surface like concrete or tiling, a skid mark shows how and why the ladder slipped. In the picture shown at right, the rubber foot in the stile end in the foreground had worn so severely that the remnants were pushed back into the hollow stile, so that it became redundant and allowed the ladder to slip, with catastrophic results for the user. The worn foot should have been replaced long before, and the employer had to pay damages to the injured painter. Ladder accidents are among the most common industrial and domestic accidents causing severe personal injury
Personal injury
Personal injury is a legal term for an injury to the body, mind or emotions, as opposed to an injury to property. The term is most commonly used to refer to a type of tort lawsuit alleging that the plaintiff's injury has been caused by the negligence of another, but also arises in defamation...
both in the USA and the UK.
See also
- Forensic Science
- Forensic engineeringForensic engineeringForensic engineering is the investigation of materials, products, structures or components that fail or do not operate or function as intended, causing personal injury or damage to property. The consequences of failure are dealt with by the law of product liability. The field also deals with...
- Forensic materials engineeringForensic materials engineeringA branch of Forensic engineering, the subject focuses on the material evidence from crime or accident scenes, seeking defects in those materials which might explain why an accident occurred, or the source of a specific material to identify a criminal...
- Forensic photographyForensic photographyForensic photography, sometimes referred to as forensic imaging or crime scene photography, is the art of producing an accurate reproduction of a crime scene or an accident scene using photography for the benefit of a court or to aid in an investigation. It is part of the process of evidence...
- Forensic polymer engineeringForensic polymer engineeringThe study of failure in polymeric products is called forensic polymer engineering. The topic includes the fracture of plastic products, or any other reason why such a product fails in service, or fails to meet its specification...
- Polymer degradationPolymer degradationPolymer degradation is a change in the properties—tensile strength, colour, shape, etc.—of a polymer or polymer-based product under the influence of one or more environmental factors such as heat, light or chemicals such as acids, alkalis and some salts...
- TireTireA tire or tyre is a ring-shaped covering that fits around a wheel rim to protect it and enable better vehicle performance by providing a flexible cushion that absorbs shock while keeping the wheel in close contact with the ground...
- Trace evidenceTrace evidenceTrace evidence is evidence that occurs when different objects contact one another. Such materials are often transferred by heat induced by contact friction....