Dr. Sangeetha Balakrishnan
PG Department of Chemistry
Women’s Christian College
Chennai – 600 006
25 November, 2016
What is Forensic Science?
‘Forensic’ – Latin forensis – “of a forum, place
Forensic science is the application of science
to matters of criminal and civil law.
An applied science; multidisciplinary and
multidimensional in nature.
The nature of science – no absolute
authoritative solutions; all it offers is objective
information on what occurred at a crime
Forensic Science – The Concept
• Based on Locard’s Principle of Exchange.
• Whenever two objects – animate or inanimate,
microscopic or macroscopic, in whichever physical
state – come in contact with each other, there would
be an exchange of materials. These materials are
known as the Physical Evidence.
• Forensic science essentially deals with the laboratory
examination of different types of physical evidence,
encountered at the scene of crime.
• Physical evidence preferred over human witness.
The History and Development of
Sir Arthur Conan Doyle
Published first novel, A Study in Scarlet, 1887.
"I've found it! I've found it," he shouted to my companion, running towards us
with a test-tube in his hand. "I have found a re-agent which is precipitated by
haemoglobin, and by nothing else . . . . Why, man, it is the most practical
medico-legal discovery for years. Don't you see that it gives us an infallible
test for blood stains? . . . . The old guaiacum test was very clumsy and
uncertain. So is the microscopic examination for blood corpuscles. The latter
is valueless if the stains are a few hours old. Now, this appears to act as well
whether the blood is old or new. Had this test been invented, there are
hundreds of men now walking the earth who would long ago have paid the
penalty of their crimes. . . . Criminal cases are continually hinging upon that
one point. A man is suspected of a crime months perhaps after it has been
committed. His linen or clothes are examined and brownish stains discovered
upon them. Are they blood stains, or mud stains, or rust stains, or fruit stains,
or what are they? That is a question which has puzzled many an expert, and
why? Because there was no reliable test. Now we have the Sherlock Holmes's
test, and there will no longer be any difficulty."
→ had a considerable influence on popularising scientific crime-detection methods
1) The Chinese book Hsi Duan Yu (The Washing
Away of Wrongs), which appeared in 1248,
provided the first association of medicine and law.
The book offered useful advice such as
distinguishing drowning (water in the lungs) and
strangulation (pressure marks on the throat and
damaged cartilage in the neck) from death by
2) Mathieu Orfila (1787-1853)
One of the first celebrated cases in forensic
science involved the 'father of toxicology',
Mathieu Orfila (1787-1853), who worked in Paris
and testified in an arsenic poisoning criminal trial
Orfila and others had developed a chemical test
to detect arsenic, the poison of choice for the
period because the symptoms, violent stomach
pains and vomiting, were similar to cholera (a
common disease of the times) and often went
3) Alphonse Bertillon (1853-1914)
Alphonse Bertillon's (1853-1914) personal
identification system using a series of
body and facial measurements for
First ID system (so to speak)!
4 )Francis Galton (1822 – 1911)
Conducted the first definitive study of fingerprints
and their classification.
1892 – Treatise entitled Finger Prints.
5) Leone Lattes (1887 – 1954)
Devised a simple procedure for determining the
blood type (A,B,O,AB) of a dried bloodstain in
Karl Landsteiner discovered blood groups in
6) Calvin Goddard (1891 – 1955)
Used a comparison microscope to determine if a bullet
was fired from a specific gun.
Published study of “tool marks” on bullets.
Father of Ballistics.
7) Albert S. Osborn (1858 – 1946)
Developed fundamental principles of document
1910 – Treatise Questioned Documents.
Was responsible for the acceptance of
documents as scientific evidence by the courts.
Forensic Labs in India
The Central Forensic Science Lab
(CFSL) in Hyderabad.
There are four central forensic laboratories in
India: Hyderabad, Kolkata, Chandigarh, and
CFSL Hyderabad is a centre of excellence in
CFSL Kolkata (oldest laboratory in India) in
Biological Sciences and CFSL Chandigarh in
These laboratories are under the control of the
Directorate of Forensic Science (DFS) of the
Ministry of Home Affairs.
Forensic Labs in India… cont’d.
Around 26 well-established forensic science labs;
mostly in the state capitals.
Many states have regional forensic science labs
in some districts under the supervision of the
state forensic lab.
Mobile Forensic Units – When evidences are too
bulky to transport, or when a rapid analysis of the
evidence becomes mandatory, mobile forensic
units are sent to the scene of crime. These units
house mini laboratories to carry out on the spot
analyses, which might aid in the further
The Organisation of a Forensic
Headed by a scientist designated as Director;
assisted by scientists at different levels – Deputy
Directors, Assistant Directors, Scientific Officers
Generally the lab is divided into divisions headed
by Deputy Directors or an Assistant Director.
All officers of the lab are empowered to
undertake examination of case exhibits and
submit reports to the court through the Director.
The Units in a Forensic Lab
0) Case Receipt Unit
- Taking over of case exhibits and handing over reports.
- The sealed parcels are accepted after examining seals, the
condition of the packet and the forwarding letter.
- Sample in the parcel sent to appropriate divisions for
- After lab examinations, the leftover portions of the samples
are forwarded to this unit to be returned to the police.
1) Biology Division
Deals with biological materials like blood,
semen, saliva, hair etc.
Also undertakes examination of skeletal
remains to find out species of origin, race,
sex, age, stature of the bio materials.
Identifies dried bloodstains and body fluids
Compares hairs and fibers
Identifies and compares botanical materials
such as wood and plants
2) Serology Division
Created as a result of the ever increasing load of
Responsible to find out the species of origin,
blood group substances, enzyme, serum protein
etc in the biological materials such as blood,
semen, saliva, epithelial cells, tissues, bones,
hairs, teeth cavity scrapings etc.
DNA profiling done here.
3) Chemistry Division
Carries out chemical analysis; both qualitative and
adulterated petroleum, fertilisers, medicines, burnt
4) Toxicology Division
Undertakes chemical analysis of all materials related
to suspected poisoning; stomach wash, vomit,
injection site etc.
5) Physics Division
Analyses building materials like adulterated cement
samples, cement-sand proportions, strength of
building materials etc.
Analysis of glass, sand, soil, paint, dirt etc.
Tool and cut mark identification, restorations of
obliterated marks/writings/numbers etc.
6) Prohibition and Excise
Analyses samples of spurious and illicit liquors,
alcoholic beverages, blood alcohol level etc.
7) Narcotics Division
Samples of all narcotic drugs and psychotropic substances
are sent to this division for analysis.
Also analyses precursor chemicals used for manufacturing
drugs and psychotropic substances.
8) Document Examination Unit
Provides the skills needed for handwriting analysis and
questioned document issues.
Also analyses paper and ink, indentations, obliterations,
erasures, and burned or charred documents.
9) Ballistics/Firearms Division
Identification of firearms
Distance of fire
Correlation between the ammunition and the firearm
Gunpowder residue analysis
10) Explosive Division
Analysis of chemical nature of material used in an
11) Photography Unit
Examines and records physical evidence at the crime scene
and at suspects' locations
12) Latent Fingerprint Unit
Processes and examines evidence for latent fingerprints
i.e. those found on surfaces
13) Polygraph Unit
Uses lie detectors, an essential tool of the crime investigator
rather than the forensic scientist
14) Voiceprint Analysis Unit
Involved in cases of telephone threats or tape-recorded
Investigators may be able to connect a voice to a particular
Other Forensic Services
Involves the investigation of unnatural, unexplained or violent death.
The forensic pathologist may conduct an autopsy.
After a human body expires, there are several stages of decomposition.
Rigor Mortis – shortening of muscle tissue; stiffening of body parts.
Occurs within the first 24 hours, and disappears within 36 hours.
Livor Mortis – results in settling of blood in areas of body closest to
ground. Begins immediately on death, and continues upto 12 hours.
Algor Mortis – results in the loss of heat by a body.
Beginning about an hour after death, the body loses heat by 1 to 1.5
degrees F. per hour until the body reaches the environmental
A medical examiner when presented with the body, will take its core
Normal body temp = 98.6 degree F.
If the deceased body temp = 85 degree F, then time since death
between 9 and 14 hours.
Other Forensic Services
Forensic Pathology …cont’d.
Potassium levels in the occular fluid also help
determine the time of death. Cells within the
eyes release K at a certain rate, and samples
are taken for analysis.
Also, during autopsy, the amount of food in
the stomach can also give an idea of the time
Other Forensic Services
Primarily involves the identification and
examination of skeletal remains, in order to
determine if the remains are human or
another type of animal.
If human, ethnicity, sex, approximate age,
and manner of death can often be
determined by an anthropologist.
A forensic anthropologist may also help to
recreate the face to aid in identification.
Other Forensic Services
The study of insects and their developmental
Can help to determine the time of death by knowing
when those stages normally appear in the insect's
The specific insects present in the body and the
stage of development of fly larvae give an idea of
how long the body has been left exposed.
Environmental influences, such as geographical
location, climate and weather conditions must be
taken into account.
Other Forensic Services
The study of human behavior and legal
proceedings in both civil and criminal cases
In civil and criminal cases, competency
often needs to be determined
In criminal trials, the evaluation of behavior
disorders is often required in order to
establish the psychological profile of a
Other Forensic Services
Involves using teeth to identify victims when
the body is left in an unrecognisable state.
Tooth enamel resists decomposition, and
outlasts even skeletal remains.
The characteristics of teeth are specific to
A forensic odontologist also investigates
The definition depends on who you ask!
Legal: That which tends to support something or show
that something is the case.
When lawyers talk about the admissibility of evidence in
court, they refer to its relevance (pertinence to the case)
and its materiality (that it tends to prove something).
Forensic Science: Evidence is anything that would make
an issue more or less likely than it would be without the
Everyday terms: Evidence is anything that tends to prove
or disprove anything.
Different Types of Evidence
1. Physical vs. Non Physical
2. Real vs. Demonstrative
3. Known vs. Unknown
4. Individual vs. Class
Physical vs. Non Physical Evidence
Physical Evidence consists of objects or
things (obtained from a scene of crime).
Non physical evidence is verbal testimony
about a crime, or it may be someone’s actions
during a crime.
Example: Someone seen running away from
a bank robbery holding a bag of money:
- the bag of money - physical evidence
- the action of running away – non physical
Real Evidence vs. Demonstrative Evidence
That which is generated by
Found at the crime scene or
elsewhere and pertains to
Eg: fingerprints left at the
scene or those obtained from
a suspect; drugs, bullets,
This is created to help
explain or clarify real
Generated after the crime
by a criminal investigator
or forensic scientist.
Eg: (i) A 3D model of a
crime scene made from
(ii) A chart or graphs from
an analytical instrument
that shows some property
of a substance.
Known vs. Unknown Evidence
Some of the most important questions that are
askedabout evidence at crime scenes are: “Do we know
where this evidence came from?”, “What is its source?”,
“Who left it?”
Successful reconstruction of a crime scene depends
upon being able to associate evidence with particular
people or objects.
The term unknown evidence always refers to the
evidence at a crime scene whose source is unknown.
Eg: A bullet found in the body of the victim of a homicide
is unknown evidence.
At the time the bullet is discovered to be an evidence,
the bullet’s source is unknown.
• A burglar breaks into a house by breaking a glass window and climbing
• On his way in, he cuts himself on the broken glass that is still in the
window, and leaves some blood on the glass.
•Some of the broken glass from the window falls to the ground, where the
burglar steps on it and gets some embedded in his shoe.
•After the crime is committed, the investigators examine the scene and find
the blood on the glass in the window.
• The blood on the glass in the window – Unknown!
• The (broken) glass in the window – Known.
• The glass on the floor around the window – Unknown. ( It’d be tempting to
say it must have come from that window; but there’s no proof. It could have
been there before the crime was committed.)
• Suspect is arrested – a search warrant to search his house obtained –
• Glass embedded in his shoes – Unknown! could have come from
•Compare glass in his shoes with glass in the window (known).
Eg: Fingerprint examiners often
testify in court that a latent
fingerprint found on an object
definitely came from a
particular finger of the suspect.
There are characteristics of each
fingerprint on each person that
make that print unique.
All fingerprints are measurably,
In most cases, the number of
possible sources is unknown.
Eg: Fiber experts testifying in
court that blue denim fibers found
at murder scene could have
come from the pants worn by the
Fibers in a given pair of pants are
Concept of individuality and uniqueness!
Individual Evidence : Evidence that could
have arisen from only one source.
Class Evidence: Evidence that could have
any number of sources.
Fingerprints (also palm prints and
footprints) Comparison of minutiae with known.
Handwriting Comparison with known handwriting
Bullets and casing Comparisons with markings or
Shoe prints and tire treads Comparison details with known
Large pieces of paint, glass or paper Fracture match or tear
match comparison with known.
Evidence Type Why Not Individual?
Tiny glass or paint fragment Too small to fracture-match; no unique
Soils Too much horizontally and vertically
Hairs and Fibres Can be individualised if DNA-Typed, else
there are no unique structural characteristics
in hairs and fibers.
Illicit drugs Can identify drug, but cannot prove that one
specimen of drug came from a particular
Fire residues Can identify class of residue (eg: gasoline),
but cannot prove that *that* gasoline came from
one particular can or pump.