Forensic footwear evidence
Encyclopedia
Forensic footwear evidence can be used in legal proceedings to help prove the identities of persons at the crime scene
. Footwear evidence is often the most abundant form of evidence at a crime scene and in some cases can prove to be as specific as a fingerprint
. Initially investigators will look to identify the make and model of the shoe
or trainer which made an impression. This can be done visually or by comparison with evidence in a database
both methods focus heavily on pattern recognition and brand
or logo
marks. Information about the owner of any footwear can be gained from the analysis of wear
patterns which are dependent on angle of footfall and weight distribution
. Detailed examination of footwear impressions can help to link a specific piece of footwear to a footwear imprint as each shoe will have unique wear characteristics.
There can also be latent impressions not easily visible to the naked eye, on many different surfaces such as floor tiles, concrete or even carpet. Detection may require the use of additional specialized light sources such as portable ultraviolet
lighting. Recovery typically includes photography as well as lifting with "gel" or "electrostatic" dust lifters.
Footwear impressions can be detected with a variety of methods including:
surface, such as mud
or as dust
deposits, which are difficult for the human eye to detect. At violent crimescenes footmarks can be left as a result of a person standing in blood and subsequently trailing it as they move around the scene.
cast
. Initially the impression is isolated by framing
the area with a solid boundary. Following this a plaster mix can be gently poured inside the frame, it is generally considered not best practice to pour directly onto the impression. In some cases where the surface is not ideal for casting prior techniques can be utilised to gain a better cast of the impression. Sand
can often be fixed in place by applying an aerosol
resin
or glue
although hair spray
is often used. Wet mud impressions can be dried using a combination of pipetting
water from the surface and applying hot air, often in the form of a hair dryer.
Footwear manufacturer, model and size:
Examination of footwear impression for "Class Characteristics" such as general outsole patterns and shapes, footwear design features and feature markings can help examiners identify the manufacturer , model and size of the footwear. This information can be used to help profile the suspect and provide leads on who may have bought or worn the footwear which created the impression.
Approximate height and wearer: Measurements of footwear impression dimensions can be used to provide the approximate height of a suspect. With shoeprint size information, investigators can refer to statistical data to approximate the height of the person since shoeprint vs. height relationship follows a normal distribution. Height can also be approximate by stride length which could be measured from a set of footwear impressions.
Activity of wearer when imprint was made: Analysis of a plastic footwear impression can also be used help determine the activity of the wearing when the imprint was made. The footwear imprint left by person is different when they are walking, running or carry heavy loads. A footwear impression left by running person will typically deeper in the heel and toe sections of the shoeprint. A person carrying a heavy load such as a body will cause deeper prints than a person not carrying anything.
Establish link between footwear impression and specific piece of footwear:
A specific piece of footwear can be linked to a specific footwear impression with careful analysis. Every piece of footwear will show different amounts of tread wear, different amounts of damage in the form of tiny cuts and nicks. These unique characteristics will also show on the impression left by the footwear.
By far the best system available is SICAR, marketed by Foster + Freeman Ltd, Worcestershire, England and currently used by Police departments in the UK, Europe, and USA. Others are available such as the Footwear Intelligence Technology (FIT) launched by the Forensic Science Service (FSS) in February 2007 and TreadMark.
Crime scene
A crime scene is a location where an illegal act took place, and comprises the area from which most of the physical evidence is retrieved by trained law enforcement personnel, crime scene investigators or in rare circumstances, forensic scientists....
. Footwear evidence is often the most abundant form of evidence at a crime scene and in some cases can prove to be as specific as a fingerprint
Fingerprint
A fingerprint in its narrow sense is an impression left by the friction ridges of a human finger. In a wider use of the term, fingerprints are the traces of an impression from the friction ridges of any part of a human hand. A print from the foot can also leave an impression of friction ridges...
. Initially investigators will look to identify the make and model of the shoe
Shoe
A shoe is an item of footwear intended to protect and comfort the human foot while doing various activities. Shoes are also used as an item of decoration. The design of shoes has varied enormously through time and from culture to culture, with appearance originally being tied to function...
or trainer which made an impression. This can be done visually or by comparison with evidence in a database
Database
A database is an organized collection of data for one or more purposes, usually in digital form. The data are typically organized to model relevant aspects of reality , in a way that supports processes requiring this information...
both methods focus heavily on pattern recognition and brand
Brand
The American Marketing Association defines a brand as a "Name, term, design, symbol, or any other feature that identifies one seller's good or service as distinct from those of other sellers."...
or logo
Logo
A logo is a graphic mark or emblem commonly used by commercial enterprises, organizations and even individuals to aid and promote instant public recognition...
marks. Information about the owner of any footwear can be gained from the analysis of wear
Wear
In materials science, wear is erosion or sideways displacement of material from its "derivative" and original position on a solid surface performed by the action of another surface....
patterns which are dependent on angle of footfall and weight distribution
Weight distribution
Weight distribution is the apportioning of weight within a vehicle, especially cars, airplanes, and trains.In a vehicle which relies on gravity in some way, weight distribution directly affects a variety of vehicle characteristics, including handling, acceleration, traction, and component life...
. Detailed examination of footwear impressions can help to link a specific piece of footwear to a footwear imprint as each shoe will have unique wear characteristics.
Types of footwear evidence
Footwear evidence can come in at least three forms, footwear outsole impressions, footwear insole impressions and footwear trace evidence.Footwear outsole impressions
Footwear outsole impressions are impressions left on an object that was caused by contact with a piece of footwear. These can left on the ground or raised surface by persons treading over it, left on doors or walls by persons attempting to kick or climb over a wall or even left on other persons after being kicked or stomped on.There can also be latent impressions not easily visible to the naked eye, on many different surfaces such as floor tiles, concrete or even carpet. Detection may require the use of additional specialized light sources such as portable ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
lighting. Recovery typically includes photography as well as lifting with "gel" or "electrostatic" dust lifters.
Footwear insole imprints
Footwear insole imprints are imprints left in the inside of footwear caused by contact from the person’s foot. Analysis of the insole imprints can be used to link a person(s) to a piece of footwear.Footwear trace evidence
Footwear trace evidence is trace evidence that is recovered from footwear. Types of trace evidence that could be recovered include skin, glass fragments, body hair, fibers from clothing or carpets, soil particles, dust and bodily fluids. The study of this trace evidence could be used to link a piece of footwear to a location or owner. DNA can be one of the contributing factors in forensic footwear evidence.Detection of footwear evidence
- Using artificial light sources to provide oblique, coaxial, and polarized light for detection of visible and latent impressions.
- Using electrostatic lifting devices to lift dusty impressions.
- Using physical or chemical enhancement methods to develop or enhance faint impressions.
Recovery of footwear impression evidence
Footwear evidence occurs most often as either footwear impressions left in a softSoft
Soft or SOFT may refer to:* Soft , a musical group* Soft!, a novel by Rupert Thomson* Soft matter, various states of matter with low resistance to external force* Soft magnetic material is a magnetic material with low coercivity...
surface, such as mud
Mud
Mud is a mixture of water and some combination of soil, silt, and clay. Ancient mud deposits harden over geological time to form sedimentary rock such as shale or mudstone . When geological deposits of mud are formed in estuaries the resultant layers are termed bay muds...
or as dust
Dust
Dust consists of particles in the atmosphere that arise from various sources such as soil dust lifted up by wind , volcanic eruptions, and pollution...
deposits, which are difficult for the human eye to detect. At violent crimescenes footmarks can be left as a result of a person standing in blood and subsequently trailing it as they move around the scene.
Lifting
Footwear impressions can be lifted from surfaces with tools such as adhesive lifters, gelatin lifters or electrostatic lifting devices.Casting
Evidence left via impressions can generally be recovered utilizing a plasterPlaster
Plaster is a building material used for coating walls and ceilings. Plaster starts as a dry powder similar to mortar or cement and like those materials it is mixed with water to form a paste which liberates heat and then hardens. Unlike mortar and cement, plaster remains quite soft after setting,...
cast
Casting
In metalworking, casting involves pouring liquid metal into a mold, which contains a hollow cavity of the desired shape, and then allowing it to cool and solidify. The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process...
. Initially the impression is isolated by framing
Framing
Framing or enframing may refer to:* Framing , the most common carpentry work* Framing or Framing effect , terminology used in communication theory, sociology, and other disciplines where it relates to the construction and presentation of a fact or issue "framed" from a particular perspective*...
the area with a solid boundary. Following this a plaster mix can be gently poured inside the frame, it is generally considered not best practice to pour directly onto the impression. In some cases where the surface is not ideal for casting prior techniques can be utilised to gain a better cast of the impression. Sand
Sand
Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...
can often be fixed in place by applying an aerosol
Aerosol
Technically, an aerosol is a suspension of fine solid particles or liquid droplets in a gas. Examples are clouds, and air pollution such as smog and smoke. In general conversation, aerosol usually refers to an aerosol spray can or the output of such a can...
resin
Resin
Resin in the most specific use of the term is a hydrocarbon secretion of many plants, particularly coniferous trees. Resins are valued for their chemical properties and associated uses, such as the production of varnishes, adhesives, and food glazing agents; as an important source of raw materials...
or glue
Glue
This is a list of various types of glue. Historically, the term "glue" only referred to protein colloids prepared from animal flesh. The meaning has been extended to refer to any fluid adhesive....
although hair spray
Hair spray
Hair spray is a common cosmetic product that is sprayed onto hair to keep it stiff or in a certain style...
is often used. Wet mud impressions can be dried using a combination of pipetting
Pipette
A pipette is a laboratory tool used to transport a measured volume of liquid.-Use and variations:Pipettes are commonly used in molecular biology, analytical chemistry as well as medical tests...
water from the surface and applying hot air, often in the form of a hair dryer.
Examination of footwear impressions evidence
Footwear impression can be used by examiners to obtain information the following information:Footwear manufacturer, model and size:
Examination of footwear impression for "Class Characteristics" such as general outsole patterns and shapes, footwear design features and feature markings can help examiners identify the manufacturer , model and size of the footwear. This information can be used to help profile the suspect and provide leads on who may have bought or worn the footwear which created the impression.
Approximate height and wearer: Measurements of footwear impression dimensions can be used to provide the approximate height of a suspect. With shoeprint size information, investigators can refer to statistical data to approximate the height of the person since shoeprint vs. height relationship follows a normal distribution. Height can also be approximate by stride length which could be measured from a set of footwear impressions.
Activity of wearer when imprint was made: Analysis of a plastic footwear impression can also be used help determine the activity of the wearing when the imprint was made. The footwear imprint left by person is different when they are walking, running or carry heavy loads. A footwear impression left by running person will typically deeper in the heel and toe sections of the shoeprint. A person carrying a heavy load such as a body will cause deeper prints than a person not carrying anything.
Establish link between footwear impression and specific piece of footwear:
A specific piece of footwear can be linked to a specific footwear impression with careful analysis. Every piece of footwear will show different amounts of tread wear, different amounts of damage in the form of tiny cuts and nicks. These unique characteristics will also show on the impression left by the footwear.
Limitations of footwear evidence
The Unabomber, Theodore Kaczynski, was known to keep shoes with smaller soles attached to the base in order to confuse investigators about the size of the suspect's feet.Footwear databases
Forensic investigators can use computerized footwear databases to quickly compare the class characteristics between footwear impression and outsole profile of footwear outsoles stored in the database. This greatly reduced the time required to match shoemarks found at crime scenes and those from criminals in custody or those stored on the database.By far the best system available is SICAR, marketed by Foster + Freeman Ltd, Worcestershire, England and currently used by Police departments in the UK, Europe, and USA. Others are available such as the Footwear Intelligence Technology (FIT) launched by the Forensic Science Service (FSS) in February 2007 and TreadMark.
External links
- Scientific Working Group on Shoeprint and Tire Tread Evidence (SWGTREAD), from the International Association for Identification