Footprints: A Forensic Analysis

Introduction

Fingerprint is a very important piece of evidence, so is Footprint. The footprint is an important piece of physical evidence found at many crime scenes, including homicide, burglary, and sexual assault. Yet, it is often overlooked in the early stages of an investigation. The most crucial aspect is the inspection and comparison of footprint impressions. These are subjected to a thorough forensic scientific assessment. Footprints may reveal information that can aid in the identification of a suspect and the crime scene. The stride dimension, location of each footprint, its shape, size, angulations and depth, interspaces and outer margins, heel creases, injuries or accidental damages provide indirect information about gait pattern, person’s height, leg length, range of body weight, and interrelated movement of the foot, ankle, leg, and body that are unique to that person.

In one Florida case, for example, a bloody shoe print was discovered on the carpet in the house of a murder victim. The print suggested that the impression was caused by a hole in the shoe. Investigators gathered and tested shoe prints from people who were known to be in the area near the time of the murder. By superimposing the bloody shoeprint from the crime scene with the test print made from the suspect’s shoe, footwear examiners were able to identify the culprit.

The Impression of a Footprint can be divided into two categories:

1. 2-D (Two Dimensional)
2. 3-D (Three Dimensional)

2-Dimensional Footprint: When the underside of a shoe collides with a hard, flat, or plane surface, such as a tile floor or concrete, this type of impression is created. The substance is frequently transmitted from the sole of the shoe to the ground. Those formed with moist dirt and blood are known as positive impressions. A favourable impression is usually obvious. These are formed in the dust or on a surface that has been lightly waxed.

3-Dimensional Footprints: “These kinds of footwear impressions are created when a person steps onto a soft surface, like mud, causing the sole of the shoe to leave a clear three-dimensional imprint.”

👣Bare footprint or Impression and shoeprints or impression are generally known as footprints.

👞They may be caused by barefoot or maybe left by footwear. These prints are known as footwear prints.

🔦The value of such evidence will, however, be proportionate to the points of identification that can be demonstrated.

🐾It is the characteristics that are unique in shape and detail that must be looked for and studied. Bare footprint or Impression and shoeprint or impression are generally known as Footprint.

👢Places where footprints can be found:

• The impressions of the foot may be caused by mud, dust, sand, snow or similar substances.
• This type of impression is three-dimensional and is referred to as a sunken foot impression.
• If the footprint is produced by the deposition of material like dust, dirt, oil, blood, colour powdery substances, etc., on smooth and hard surfaces, giving rise to a two-dimensional print, it is known as a surface footprint.
• They are generally found indoors.
• Footprint may also be produced by lifting dust or liquid material, in which case a negative print will be left on the surface.

👞Location of Footprints

• At the scene of the crime,
• Around the place of occurrence,
• Along the route taken by the culprit, both at the time of ingress and egress.
• At the places where the culprits gathered together for planning before action and for sharing the booty.
• Footprints may be found in the fields, courtyards, floors of rooms, walls, staircases, roofs, tables and chairs, papers, boxes, drain pipes, etc.
• If the culprit has visited a garage, he is likely to leave prints on the greasy surface of the garage floor,
• If the culprit gets his foot or footwear smeared in blood, he is likely to leave prints in blood.

Preservation

The following instructions should be followed:
• Footprints on the walls should be covered with paper.
• If the footprints are on easily removable articles, these should be taken into custody.
• If the footprints are inside the room and cannot be immediately removed or recorded, then the room should be locked.
• If the prints are in open places, where persons ignorant of the occurrence generally come and go, it may be necessary to post a guard besides covering the prints.

👢Collection Of Footprints

PHOTOGRAPHY

General photographs showing the evidence position in relation to the rest of the scene, as well as high-resolution images of the individual imprints or impressions, are taken in the instance of impression evidence. Examiners may use other light sources or chemical enhancers to capture as much detail as possible, particularly when dealing with latent imprints. 35mm SLR is considered the best camera. The following points should be kept in mind:

• All prints and impressions should be photographed before attempting any other method.
• Thus, photographs are first taken of both surface prints and sunken impressions.
• A flash should be used even in sunlight so that the details are clearly defined.
• Place a ruler along the length of the print so that the proper scale of the photograph can be determined.
• Identification details, such as date, case number, and signatures of the investigator and witnesses, may be written on a piece of paper and placed near the print.

TRACING

Tracing is the crudest but the easiest way of recording surface footprints. A glass or celluloid sheet and a glass marking pencil or an oil-based pen are used for tracing the outlines of the footprint.

The following procedure should be followed:
✔ The sheet of glass or celluloid sheet should be kept over the footprint, as close as possible, but taking care that it does not actually touch it.
✔ The lines should be drawn as thin as possible.
✔ The part of the foot of which the tracing is to be made, the tip of the pen and the eye should be in a line to avoid distortion.
✔ The clear outline of the different parts of the footprint should be shown in thin continuous lines. The faint and doubtful outline may be shown with dotted lines.

LIFTING

i.) Photo Bromide Paper

Surface footprints can be lifted if the prints are caused by deposition of dust material. If the dusty print is white or light in colour, a black photo bromide paper is used.
If the print is of black dust, then photo bromide paper is fixed without exposure to light, and the print is lifted as above.
The black paper is obtained by exposing it to light and then developing and fixing it.
It is placed over the print and pressed uniformly. The dusty print gets attached to the gelatin surface.
The emulsion side will attain a tacky surface.

(ii) Static Electricity lift

Often, dust or dirt on shoes or bare feet leaves surface prints on rugs, mats, cloth, etc., because of colour or texture, the prints are not visible.
A black vinyl plastic charged with a high voltage can also be used to lift such prints. The static charge generated after discharging the initial high voltage attracts dust particles, giving rise to negative print.

(III) Adhesive And Gelatin Lifters

Impression-size adhesive and gelatin lifters are used to lift dust and residue imprints, wet-origin impressions, and fingerprint powder impressions.

Gelatin lifters come in white, black, and transparent. White lifters provide more contrast when combined with dark-colored powders to enhance impressions. Black lifters contrast nicely with light-colored powders and residual impressions. Transparent lifters do not generally give strong contrast. Photograph gelatin lifts of residue impressions as soon as possible after collecting.

Casting

Casting can capture any plastic or three-dimensional footwear or tyre impressions. Casting involves the use of a powdered stone substance, such as dental stone, that is combined with water and poured into the impression. When it dries, this process generates a three-dimensional model of the impression. Casts can be made with plaster of Paris, wax, resin, sulphur and various other materials.

👡Preparation of surface

✅ If the impression is in soft dust or sand, then a thin layer of shellac dissolved in alcohol is spread on the surface by means of a sprayer. The shellac is carefully sprayed from a distance so that the air pressure will not disturb the detail of the impression.
✅ Mount a metallic or wooden frame around the impression to prevent the liquid plaster from escaping.
✅ After several minutes, the shellac will have hardened, leaving a thin film on the surface.
✅ Extraneous matters such as grass, twigs, and stones falling after the impression is made should be removed without disturbing the impression.
✅ A thin layer of talcum powder or mineral oil is sprinkled on the layer of shellac, which will permit the peeling of the shellac without affecting the cast.

👞Preparation of plaster

✔ Mix the plaster in a container partially filled with water until water can no longer absorb powder.
✔ Make sure that no lumps are present and a thick creamy consistency of the mixture is obtained.
✔ 7:4 is the best proportion of plaster of Paris and water.

👡Pouring of plaster

• Pour the mixture gently into the impression. A spoon should be used to pour the mix from a low level and to spread the plaster evenly. Air bubbles should be prevented.
• When the layer of plaster is almost one-half inch thick, place small twigs or sticks in a criss-cross pattern to reinforce the cast.
• A thin wire mesh could also be used in place of sticks. A second layer of plaster mixture should follow this until the cast is about one inch thick. The plaster is allowed to set for fifteen minutes. The setting of the cast is indicated by the rise in its temperature, which can be felt by touching the cast surface.
• In order to fasten the process of hardening, one half teaspoon full of common salt may be added to the water before adding plaster, whereas, if sugar or borax is added to the mixture, the setting time gets retarded.

👣Collection of comparison print

• It is always better to compare crime scene footprints with the comparison print made on a similar surface. The suspect should be made to walk on the soft earth to leave a sunken impression, and a cast as described above should be obtained. Inking the foot of the suspect and then transferring the inked impression onto paper, obtaining surface prints for comparison. To get an accurate idea of the formation of the soles of the feet, four to five different prints are taken differently:
• Normal standing position,
• Standing position with pressure on the inner side,
• Standing position with pressure on the outer side,
• When walking, and
• When jumping.

Enhancement of the Footprints photograph

Imprints and impressions can be enhanced or improved to bring out more minute details. A digital enhancement program, such as Adobe Photoshop®, can be used to increase the quality of a photographed tyre track, for example. Fingerprint powders and chemical stains or dyes can improve image colour or contrast with the background. This allows evidence that has been lifted or cast to be photographed or scanned.

Evaluation and Comparison

Every impression has an individual entity that cannot be duplicated. Examiners employ instruments such as dividers, callipers, special lighting, and low magnification throughout the examination and comparison. Examiners evaluate the different parts of the tread design and the length and width of the impressions, then compare those dimensions to what is visible in the crime scene print or impressions. Low magnification and specific lighting are sometimes used to assess whether certain qualities are incidental or a result of the production process. Examiners conduct side-by-side comparisons by placing the known shoe or footprints alongside the crime scene print to analyze related areas.

When analyzing footprints for identification purposes, several vital characteristics are examined. These include the size of the footprint, the shape and height of the arch, the alignment and length of the toes, and any distinctive patterns present on the sole of the foot. Additionally, investigators look for scars, injuries, or deformities that may be visible in the footprint, as well as wear patterns caused by habitual walking or footwear. The most significant evaluation of a footprint is identifying a gait pattern for the direction line, the walk line, the foot line, the foot angle, the step angle, and so on.

👣Identification characteristics

It is well established that every footprint has an individuality, which cannot be duplicated. The individuality in a given print is established by studying the following characteristics:
🔍Dimension: The dimension cannot be given too much significance. Nevertheless, it should be noted. If the dimensions vary to a considerable extent, then it can be deduced that the suspect could not have left the questioned print.
🔍General shape: The shape of the foot may have remarkable variations. It may be a normal, flat, club-shaped, bow-shaped, broken bridge, or abnormal.
🔍Pattern: Sometimes ridge patterns may be noticed on the prints and impressions. Their study may reveal identifying characteristics.
🔍Margins: Sometimes the margin of the bare footprints is highly characteristic. The margins consist of the outline of the heel and the inner and outer boundary lines of the foot. The heel may be oval or round; the outer margin may be straight, bulging outward or inward.
🔍Toe marks: The shapes and sizes of the toes, their interspaces, and alignment vary greatly. Long and short toes, missing toes, an extra toe, etc., may be highly characteristic
🔍Crease, phalange, cut marks, etc. The shape, size, and position of the phalanges of the toes, crease marks, or cuts may be highly characteristic.

👣Khoji System of Identification

✅There exists a tribe known as ‘Khoji,’ dwelling in parts of Rajasthan, Gujarat, and Punjab, whose hereditary profession is to study the footprints of persons and the marks left by animals.
✅Their services are utilized by the police to track culprits or stolen animals. These trackers can tell whether the footprint of the animal is a fresh one or a few hours old or, for that matter, even a few days or a few months old.
✅The khoji used different terms to describe various parts of the foot. The terms used by them are described in the following figure: