Category Archives: Biometrics

Chelioscopy{LIP PRINT}

By @forensicfield

INTRODUCTON

Lip prints, like fingerprints are unique to an individual and can be easily recorded. Identification plays a major role in any crime investigation.

The pattern of wrinkles on the lips has individual characteristics like fingerprints.

Cheiloscopy is a forensic investigation technique that deals with identification of humans based on lips traces.

Use Of Lip Prints In Crime Detection

Lip prints have the same value as Dactyloscopic traces.

Just like finger print and teeth, lip print can be used as tool for identification.

Lip prints are unique and do not change during life of a person.

They can be most frequently seen during murders, rapes and burglaries.

Traces with clear lines and individual elements enable individual identification of human beings.

In their character they are similar to other chemical and biological traces.

What Is Vermillion Zone?

The lips are the junction between the skin of the face which is Para keratinized stratified squamous epithelium and  the mucosa of the oral cavity which is moist non-keratinized to Para keratinized stratified squamous epithelium.

Between these two areas lies a transitional zone of reddish tissue known as the vermillion zone of the lip.

It is this vermillion zone which is commonly denoted as ‘lips’ in forensic identification procedures.

History

  • The biological phenomenon of systems of furrows on the red part of human lips was first noted by anthropologists R. Fischer in 1902.
  • In 1932, one of the France′s greatest criminologist Edmond Locard, recommended the use of lip print for identification of a person.
  • The idea of using lip print for identification was first suggested by Le Moyne Snyder in the year 1950. He introduced a case in which lip prints helped the crime scientist in an unusual way.
  • Dr. Martins Santos in 1960 proposed that these lip characteristics could be used in personal identification and devised a simple system for classifying lip prints.
  •  In 1967, Suzuki made a detail investigation of the measurement of lips, the use and the colour of rouge and method of its extraction to obtain useful data for forensic application.
  • Later in 1971 Suzuki and Tsuchihashi, conducted a study and they devised their own classification. 
  • Mc Donell in 1972 conducted a study on lip prints between two identical twins and reported that two identical twins seemed to be indistinguishable by every other means but they had different lip prints.
  • Cottone in 1981, reported in his book Outline of Forensic Dentistry, that Cheiloscopy is one of the special techniques used for personal identification.
  •  In 1990, Kasprzak conducted research for the period of 5 years on 1500 persons to elaborate the practical use of lip prints.

Anatomy & Morphology of Lips

Lip of human being consists of 2 parts

1.)  Upper Lip 

2.)  Lower Lip

Both these upper & lower lip are divided into six different regions, which are as follows-

Where,  UL – Upper Left,   UM – Upper Middle,   UR – Upper Right
                LL – Lower Left,   LM – Lower Middle,   LR – Left Right.

Other features of Lips

Following features are also present in lips which is use for individualization & comparison, which are as follows:

Classification

In 1967 Santos was the first person to classify lip grooves. He divided them in to four types namely:

  • Straight line
  • Curved line
  • Angled line
  • Sine-shaped line

Tsuchihashi Classification

Suzuki and Tsuchihashi, in 1970, devised a classification method of lip prints as follows:

  • Type I : A clear-cut groove running vertically across the lip.
  • Type I′ : Partial-length groove of Type I.
  • Type II : A Branched groove.

It include branch grooves across the whole lips.

  • Type III : An intersected groove.

It include grooves which are intersecting each other.

  • Type IV : A Reticular pattern

In this type lips contains rectangular grooves.

  • Type V : Other patterns.

Grooves which about fall in any of the above four categories.

Another type of Classification

Another Four types are also used to classified Lip Prints

Lip Groove Types

Where,

A – Complete Vertical;                   B – Incomplete Vertical;

 C – Complete Bifurcated;            D – Incomplete Bifurcated;         

 E – Complete Branched;                F – Incomplete Branched;           

 G – Reticular Pattern;                     H – Cross Form;

 I – Horizontal / Complete Horizontal;   J – Horizontal With Other Forms.

 Forms Of Lip Prints Found On Crime Scene

These 3 types of Lip Prints can be found at the scene of crime. Lip prints are available particularly in the following forms-

1.) Visible Lip Prints – These are the Lip Prints which are visible to the unaided eye and it do not need any further development for its visualization.

2.) Latent or Hidden Lip prints – These are the Lip Prints which are not visible to human eye. It requires further development processes for its visualization.

3.) 3-D or Plastic Lip Prints – These are the Lip Prints which are found on soft, gel like surface (wax or butter). They are visible to unaided eye but sometimes need develop processing for photography.

How To Search Lip Prints On Crime Scene

  • The search for possible Lip Prints needs a systematic and narrowly approach to the suspected areas.
  • A magnifying lens is useful to locate and judge the quality of the Lip Prints.
  •  Traces of lips should be looked for on cutlery and crockery items, on the window or door glass and on photograph or letters. Lip print may also appear on side by side with tooth marks on food products. In practice, lip prints have also seen in the windows, painting, doors, plastic bags and cigarette ends.
  • Observation under white light may reveal latent Lip Prints that can be photographed without any further treatment.
  • Lip Prints can frequently be seen by holding the flashlight at low angles so that the surface is observed under oblique lighting.
  • In some cases, latent print can often be detected using episcope coaxial illumination. The print is, therefore, visible as dark ridges against a light background.

The process is concerned with recognition, examination, identification, individualization, and evaluation.

Development of Lip prints

1.} Powder Method

2.} Chemical Method

3.} X-Ray Method

1.}  Powder Method

Following methods are used for developing Lip Prints:-

A powder technique is usually used to identify latent prints on nonporous surfaces such as glass, marble, metal, plastic, and finished wood.

When powder is distributed on the surface, it adheres to the residue deposited from the finger’s touch, allowing investigators to find the print.

  • Following Powder Method Can Be Used To Develop Lip Print-
  • Aluminum Powder Method
  •  Magnetic Powder Method
  • Plumb Carbonate Powder (White Powder)

2.} Chemical Methods

Crime Scene Investigators Often Use Chemical Methods To Locate The Print Such As;

  • Iodine Fuming [must be photographed quickly because Print fades quickly after the fuming takes place],
  • Silver Nitrate (Agno3) [works well on impressions left in cardboard and paper-like surfaces],
  • Ninhydrin, [reacts with the oils in the print’s residue to create a bluish print],
  • Lysochrome Dyes (Sudan 3 Dye And Oil Red ‘O’ Dye/ Red ‘O’ Dye),
  • Small Particle Reagent (SPR).

When one of these chemicals comes into contact with the chemicals present in the Lip Prints residue (natural oils, fats), the print become visual.

3.} X-Ray Method

  •  Lead powder distributed on suspected area with the help of brush.
  •  Dusted area should X-Rayed and then photographic film of X-Ray should treat with required chemicals.

Development of lip prints on Multi colored surface

Following 3 methods can be used to develop lip prints on multicolored surface –

  • Sudan Black Reagent – it can applied directly to the print.
  • Yellow Fluorescent Powder (Illumination through UV light)
  • Nile Red Reagent

Lifting of Lip Prints

There Are 2 Methods Are Applied For Lifting Of Lip Prints-

  • Photographic Method – The developed prints should always be photographed by using a fixed focus camera or variable zoom photographic camera with the help of measuring.
  • Transparent Tape Method – Powder dusted lip prints can be lifted with the help of transparent tape from a liquid and hard surface.

Collection of Lip Prints from Suspect

  • Lip prints can be recorded in a number of ways.
  • Photographing the suspect′s lips.
  • Applying lipstick, lip rouge, or other suitable transfer mediums to the lips and then having the individual press his or her lips to a piece of paper or cellophane tape or similar surface.
  • By having the subject impress his or her lips (without lipstick or other recording medium) against a suitable surface and then processing these prints with either conventional finger print developing powder or with a magna brush and magnetic powder.
  • On a non-porous flat surface such as a mirror they can be photographed, enlarged and overlay tracings made of the grooves.

Examination and Comparison

Generally two prints are required for comparison :

  • A lip print recorded from the Scene Of Crime (SoC);and
  • A lip print which has been taken from suspect.

Both compared on the basis of individual characteristics of Lip Prints.

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Fingerprints

By @forensicfield

PRINCIPLES OF FINGERPRINTS

1. A fingerprint is an individual characteristic.

  • No two fingers have the same fingerprint.
  • Identical twins are similar but not identical.

2. Fingerprint remains unchanged during a lifetime.

3. Fingerprint has general ridge patterns that permit them to be classified.

BIOLOGICAL PRINCIPLES

Fingerprints follow three basic biological principles:

PATTERN TYPE: – All fingerprints can be classified into pattern types.

UNIQUENESS:-Each fingerprint is unique, no two people have the same fingerprints.

PERMANENCE: -Fingerprints are unchanging from 3 months fetal life until decomposition.

DEVELOPMENT OF FINGERPRINT

Fingerprint ridges are formed during the third to fourth month of fetal development and their formation completed by the sixth months.

Chance Print

The Fingerprint Left By The Culprit At The Crime Scene Are Better Known As “Chance-prints” And Very Often Found Mainly Of Three Types:

1.) Plastic Prints / Impression

These Occur When A Finger Or Palm Touches Or Presses Against Plastic Material.

These Prints Are Usually Found On Materials Such As Soap, Mud, Pitch, Melted, Wax, Fresh Paint, Putty, Butter, Gum Of Envelop, Grease, Adhesive Tape, Thick Dried Blood, Negative Film, Plastic, Explosive Etc.

Fingerprint Found On These Surfaces Are Of Three Dimensional Natures.

2.) Patent Fingerprints / Visible 

These are prints that are created from the finger contaminated with foreign materials such as blood, paint, grease, ink, oil, dust, mud, soot, dry flour, and face-powder.

3.)  Latent Prints / Invisible

Latent or invisible fingerprints are the most often found at the crime scene on object with polished or smooth-surfaces.

These prints are formed by a combination of dust. Latent prints include those which are invisible to the unaided eye and all others that are visible but only properly examined after development.

Significance

Uniqueness:- The characteristics features of a fingerprint are so unique that they are not exactly repeated in any other fingerprint or part of one.

Infallibility:- Fingerprints are now universally recognized as an infallible means of personal identification and identification of criminals.

Durability:- A fingerprint remains unchanged throughout the life of an individual.

Simplicity:-  Records of millions of persons can be kept and retrieved easily with the help of a computer. 

Searching Of Fingerprint From The Scene Of Crime

Location

  • When a criminal acts, he cannot avoid leaving clues in the form of fingerprints unless he wears gloves or something else for protection.
  • The following locations are very much common to find fingerprints:-
1.) The Crime Scene
  • Furniture, Almirah, Boxes, Glass Articles, Crockery, Fridge, Utensils, Bottles, Etc. Should Be Carefully Examined.
  • Walls, Windows, Vehicle, Floor, Doors, Light Switches, Circuit Breakers and Fuses Should Always Be Examined.
  • Good Prints Are Often Found On Glass, China Clay Articles Polished Or Painted And Other Smooth Surfaces Like Photography Paper, Negative Film, Adhesive Tape, Carbon Paper, Etc.
2.)  Point of Entry
  • If A Door Was Broken Or Forcefully Opened, Fingerprints May Be Found On The Locks, Knobs, Handles.
  • If a window was broken, search for pieces of broken glass which may contain fingerprints.
  • Fingerprints May Be Left On The Window, Window Frame, Window Steel And Jamb.
3.)  The Vehicle
  • The Transport Vehicles such as Cars, Jeeps, Motorcycles, Scooters, etc. are likely to bear fingerprint of the culprit or their occupants.
  • Steering, Wheel, Back Review Mirror, Lower Parts Of Dikki And Window Glasses, Etc. may contain fingerprints.
4.) Objects Belonging To The Culprit
  • The culprits very often leave some objects belonging to them which may have excellent chances of bearing fingerprints.
  • Such Objects May Include Shoes, Watch, Tools, Weapon Of Offence, Torch, Liquor Bottles, Poison Bottle, Gas Cutters Assembly, Container Of Fuel Oil Especially In Cases Of Arson, Etc.
5.) Human Bodies
  • Recent techniques have made possible to develop fingerprints on human bodies.
  • Such Fingerprints Are Usually Located On The Skin At Neck, Breasts, Thighs, Wrists And Ankles Regions.

When And How Is Fingerprint Analysis Used?

  • Identification of criminals whose fingerprints are found at the scene of crime.
  • Providing biometric Security
  • Identifying amnesia Victims and Unknown deceased
  • Conducting background checks
  • Identification of missing persons or in cases of kidnapping.
  • Identification of unconscious persons.
  • In mistaken identity.
  • Detection of bank forgeries.

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Biometrics

INTRODUCTION

✴ The term “biometrics” is derived from the Greek words “bio” (life) and “metrics” (to measure).
✴ Biometrics is the technical term for body measurements and calculations.
✴ Biometrics is the measurement and statistical analysis of people’s unique physical and behavioral characteristics.
✴ Biometrics allows a person to be identified and authenticated based on a set of recognizable and verifiable data, which are unique and specific to them.
✴ Biometrics authentication is the process of comparing data for the person’s characteristics in order to determine resemblance.

CHARACTERISTCS

1. UNIVERSAL
2. UNIQUE
3. INVARIABLE
4. RECORDABLE
5. MEASURABLE

HISTORY OF BIOMETRICS

🔘1858 – First systematic capture of hand images for identification purposes is recorded.
🔘1870 – Bertillon develops anthropometries to identify individuals.
🔘1892 – Galton develops a classification system for fingerprints.
🔘1896 – Henry develops a fingerprint classification system
🔘1903 – NY State Prisons begin using fingerprints.
🔘1960s – Face recognition becomes semi-automated.
🔘1960 – First model of acoustic speech production is created.
🔘1963 – Hughes research paper on fingerprint automation is published.
🔘1974- First commercial hand geometry systems become available.
🔘1976 – First prototype system for speaker recognition is developed.
🔘1986 – Exchange of fingerprint minutiae data standard is published.
🔘1988 – First semi-automated facial recognition system is deployed.
🔘1991 – Face detection is pioneered, making real time face recognition possible.
🔘1992 – Biometric Consortium is established within US Government.
🔘1994 – Palm System is benchmarked.
🔘1996 – Hand geometry is implemented at the Olympic Games.
🔘1996 – NIST begins hosting annual speaker recognition evaluations.
🔘1997 – First commercial, generic biometric interoperability standard is published.
🔘1998- FBI launches COOlS (DNA forensic database).
🔘1999 – FBI’s IAFIS major components become operational.
🔘2001 – Face recognition is used at the Super Bowl in Tampa, Florida.
🔘2002 – ISO/IEC standards committee on biometrics is established.
🔘2004 – First statewide automated palm print databases are deployed in the US.
🔘2008 – U.S. Government begin coordinating biometric database use.
🔘2010 – U.S. national security apparatus utilizes biometrics for terrorist identification.
🔘2011 – Biometric identification used to identify body of Osama bin Laden.

TYPES OF BIOMETRICS

Biometrics Can Be Divided Into Three Main Categories Of Characteristics:
1. BIOLOGICAL
2. MORPHOLOGICAL
3. BEHAVIORAL

⏩DNA MATCHING

The identification of an individual using the analysis of segments from DNA.

👂EAR

The identification of an individual using the shape of the ear.

👀EYES – IRIS RECOGNITION & RETINA RECOGNITION

👁IRIS RECOGNITION- The use of the features found in the iris to identify an individual.
👁RETINA RECOGNITION- The use of patterns of veins in the back of the eye to accomplish recognition.

👱‍♂️FACE RECOGNITION

The analysis of facial features or patterns for the authentication or recognition of an individuals identity.

🤘FINGERPRINT RECOGNITION

The use of the ridges and valleys (minutiae) found on the surface tips of a human finger to identify an individual.

👋FINGER GEOMETRY RECOGNITION

The use of 3D geometry of the finger to determine identity.

🤚HAND GEOMETRY RECOGNITION

The use of the geometric features of the hand such as the lengths of fingers and the width of the hand to identify an individual.

🙌VEIN RECOGNITION

Vein recognition is a type of biometrics that can be used to identify individuals based on the vein patterns in the human finger or palm.

👃ODOUR

The use of an individuals odour to determine identity.

✍SIGNATURE RECOGNITION

The authentication of an individual by the analysis of handwriting style, specifically the signature. Technology is available to check two scanned signatures using advances algorithms.

👩‍💻TYPING RECOGNITION

The use of the unique characteristics of a persons typing for establishing identity.

🗣VOICE / SPEAKER RECOGNITION

There are two major applications of speaker recognition:
🙊Voice – Speaker Verification / Authentication
🙊Voice – Speaker Identification
✔In forensic applications, it is common to first perform a speaker identification process to create a list of “best matches” and then perform a series of verification processes to determine a conclusive match.
✔Voice recognition analyzes audio input for specific patterns in speech or sound. Each voice, or common noise, has a recognizable wavelength pattern that can aid in identification of a specific individual.

🚶‍♀️👣GAIT

The use of an individuals walking style or gait to determine identity.

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E-BOOK ON BIOMETRICS

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EAR PRINT

Introduction

In recent years, Earprint👂 analysis has been developed in the field of Forensic Science with the aim of converting it into an identification tool. The possibility of using the external ear👂 as a tool for establishing the unique identity of individuals was first recognized by Bertillon who included the same in the system he developed in 1893. Since then several studies on its range of peculiarities in morphology have emerged especially to correlate it with the field of personal identification.

👂The ear has been used as a tool for human identification since the late 19th century when Alphonse Bertillon utilized the ear as one of the eleven anthropometric measurements for his manual system of identifying individuals.
👂An ear print is a two-dimensional reproduction of the auricle, which can make contact with various surfaces and can produce a print like a rubber stamp.

STRUCTURE OF THE EAR

DIFFERENT SHAPES OF EAR (LOBULE)

A Tool For Personal Identification

✔As early as in eighteenth century the complex shape of ear had attracted the attention of early Physiologists “Lavater”.
✔On the basis of the various ear features he tried to classify the behavioral nature of human.
✔The earliest reference to individuality of external ear was made by Bertillon who mentioned in his book that “it is almost impossible to meet with two ears which are identical in all their parts.”
✔He had formulated a system based on anthropometry to prevent repeat offenders from concealing their identity.

REASONS TO CHOOSE EAR RECOGNITION OVER OTHER TECHNOLOGY

a) Ear biometrics are convenient and because their acquisition tends to be perceived as less invasive.
b) It is accurate and allows for high enrolment and verification rates.
c) It does not require an expert to interpret the comparison result.
d) It can use with existing cameras and image capture devices will work with no problems.

EAR PRINTS AS AN EVIDENCE

✅Burglars often listen at windows and doors, leaving an ear print behind, which, just like a finger print, can be used to trace them.
✅In one out of every twenty burglaries the burglar leaves an earprint behind, at least this seems to be the case in and around Leiden.

HOW TO DEVELOP LATENT EAR PRINTS

Three methods were used to develop ear prints

1. POWDERING METHOD
Ear prints developed with Powdering method

2. NINHYDRIN METHOD
Ear prints developed with ninhydrin

3. IODINE FUMING METHOD
Ear prints developed with Iodine fuming.

VALIDITY OF THE EARPRINT AS FORENSIC EVIDENCE

👂The forensic validity of the ear print is based on the possibility of identifying a particular ear print as belonging to a particular subject.
👂In practice this can serve to rule out a subject as a suspect, to increase the evidence against a particular suspect or even, if there are no suspects, to search for suspects in future databases.

The Limitations of The Method

👉Surface ,on which print is made.
👉Angle at which the ear was applied to the surface.
👉This may be due to the manner in which the prints are made.
👉Clarity.

CASE STUDY – 1

👂Mark Dallagher, who was convicted of murder in West Yorkshire in 1998. He was alleged to have left impressions of his ears on a dining room window before murdering Dorothy Woods, 94, in Huddersfield.
👂Ear print evidence was pioneered by Inspector Cor van der Lugt, of the Dutch police.
Police found two prints on a window, and sent them to Dutch Policeman Van Der Lugt.
👂Inspector Van Der Lugt, compared the prints of Dallagher’s ears with those of eight people taken at random. Killer’s prints matched with print found on the window “exactly”.

CASE STUDY – 2

👂A 26-year-old Georgian thief has been found responsible for up to 80 robberies in the French city of Lyon after leaving his ear prints behind at some 80 robberies.
👂He targeted student housing and would press his ear up to the door to check that residents had left, leaving behind the incriminating evidence.
👂The man was caught red-handed in February, a police source said. But subsequently investigations showed his ear prints on the front doors of the scene of some 80 similar thefts in the central French city.

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Ear print (easy notes)

👞FOOTPRINTS👣

Introduction

👣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.

👡Preservation

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

1.) PHOTOGRAPHY – Generally, all prints and impressions should be photographed before attempting any other method.
Thus photographs are first taken of both surface prints and sunken impressions.
While taking a photograph one should:
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.

2.) 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 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.

3.) LIFTING
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.

4.) Casting – Casting can lift sunken foot impressions. 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.

👣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 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:

Khoji System of Identification

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Footprint