Because forensic science is based on physical evidence, forensic investigators analyse crime sites or crime scenes for physical evidence like fingerprints, blood, lip print, Footprint, etc., in order to identify the perpetrator and solve crimes. 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.
At 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 at 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:
- 2-D (Two Dimensional)
- 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 a 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 forms of footprint impressions occur when a shoe is impressed into a soft material such as mud, sand or snow.
👣Bare footprint or Impression and shoeprint or impression is generally known as Footprint.
👞They may be caused by bare foot, or may be left by footwear. These prints known as footwear prints.
🔦The value of such evidence will however proportionate to the points of identification, which can be demonstrated.
🐾It is the characteristics that are unique in shape and detail, which must be looked for and studied.Bare footprint or Impression and shoeprint or impression is generally known as Footprint.
👢Places where footprints can be found:
- The impressions of the foot may be caused in mud, dust, sand and snow or like substances.
- These type of impression is of three dimensional type and referred as sunken foot impression.
- If the footprint is produced by deposition of material like dust, dirt, oil, blood, colour powdery substances, etc., on smooth and hard surface, giving rise to a two dimensional print, it is known as 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 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, staircase, 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.
The following instructions should be followed:
• Footprints on the walls should be covering with paper.
• If the footprints are on easily removable articles, these should be taken into custody.
• If the footprints are inside the room and they 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
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 as best camera. Following points should be keep 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, signatures of the investigator and witnesses, may be written on a piece of paper and placed nearby the print.
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 is 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.
i.) Photo Bromide Paper:
Surface foot prints 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 exposing to light, and the print lifted as above.
The black paper is obtained by exposing the paper to light and then developed and fixed.
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 leave surface prints on rugs, mat, 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 lifting such prints. The static charge generated after discharging the initial high voltage, attracts dust particles giving rise to negative print.
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, stones fallen after the impression is caused, 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 container partially filled with water until water can no longer absorb powder.
✔ Make sure that no lumps present and a thick creamy consistency of 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 mixture 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 on it 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 that can be felt by touching the cast surface.
- In order 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 the 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 on a paper obtain surface prints for comparison. In order to get a true idea of the formation of the sole of the feet, four to five different prints are taken in different manner:
- 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 Footprints photograph
Imprints and impressions can be enhanced or improved to bring out more minute details. A digital enhancement programme, 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 footmark has an individual entity that cannot be duplicated. Examiners employ instruments such as dividers, calipers, special lighting, and low magnification throughout the examination and comparison. Examiners evaluate the different parts of the tread design, as well as the length and width of the impressions, and 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 analyse related areas. Many features for identifying traits, Cycling toes, long and short toes, missing toes, partially chopped toes, and injured toes can all provide useful traits and may be adequate for identification. The phalange of the toes creates phalange markings; their existence, position, forms, and sizes are frequently identifiable qualities. They are usually encountered in the foot mark. Because it contains multiple identifying features, it is feasible to identify a footwear mark even if it is incomplete. Heel markings alone can occasionally identify a shoe. The most significant evaluation of a footprint is the identification of a gate pattern for the direction line, the walk line, the foot line, the foot angle, the step angle, and so on.
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 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 margin of the bare footprints are highly characteristics. The margins consist of the outline of the heel and the inner and the outer boundary line 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 inter spaces and alignment vary greatly. Long and short toes, missing toes, an extra toe etc., may be highly characteristics
🔍Crease, phalange, cut marks etc.: The shape, size 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, Gujrat and Punjab, whose hereditary profession is to study the footprints of the 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 few months old.
✅The khoji’s used different terms to describe various parts of the foot. The terms used by them are described in the following figure: