Forensic science refers to scientific disciplines applied to legal matters. There are many branches including forensic pathology, toxicology, DNA analysis, and ballistics. Forensic scientists analyze physical evidence but do not directly solve crimes. Their results are presented in court. Forensic chemistry involves applying chemical principles to investigations like drug analysis, arson, trace evidence analysis, and gunshot residue analysis. Identification, classification, and individualization are used to determine if a questioned sample matches a known one. Forensic scientists must understand both science and the legal system to properly analyze evidence and present findings in court.

1. Dr. G. Maya
Assistant Professor of Chemistry
Govt. Polytechnic College Cherthala

2. Forensic Science
•The term “forensic science” refers to a group of
scientific disciplines which are concerned with the
application of their particular scientific area of
expertise to law enforcement, criminal, civil, legal,expertise to law enforcement, criminal, civil, legal,
and judicial
matters.
•Forensic science is the application of scientific
principles to matters involving law.

3. Branches of Forensic science
Forensic Pathology
Forensic anthropology
Forensic odontology
Forensic entomology
Forensic toxicology
Forensic chemistry
Forensic DNA analysis
Forensic Ballistics
Forensic Finger printing
Forensic Psychiatry

4. The forensic scientists do not directly solve crimes.
simply analyze the physical evidence.
Physical evidence includes all objects collected and
packaged at a crime scene that will be subsequently
analyzed in a crime laboratory.
Role of Forensic Scientist
analyzed in a crime laboratory.
The results should be recorded systematically to
submit before court.
Role of expert witness

5. Forensic chemistry is a specialized area of
forensic science involving the application of
Forensic chemistry
chemical principles and techniques to the
field of forensic investigation

6. Areas of Forensic Chemistry
Drug analysis
Arson
Trace analysis
Soil analysis
Gunshot residue analysis etc.

7. THEORY OF FORENSIC ANALYSIS
Forensic analysis may be performed to
(1) identify a questioned sample or
(2) compare a questioned sample to a known
sample for the purpose of determining the
source or origin of the sample

8. A forensic analysis follows the order of
1. Identification
2. Classification2. Classification
3. Individualization

9. Identification
Two types of analysis
Presumptive – provides enough information
to narrow down the searchto narrow down the search
Confirmatory-identify a questioned sample
absolutely

10. usually quick and inexpensive to perform.
In drug analysis, when presumptive analyses
Presumptive analyses
are negative, they exclude potential drug
candidates;
when they are positive, they direct the
forensic scientist toward viable
confirmatory analyses.

11. identify a questioned sample absolutely
required for court and must be performed to convict
someone for possession of an illegal substance.
use the unique chemical or physical properties of a
Confirmatory analyses
substance for the purpose of identification.
require more time and expense than presumptive
analyses.
require the use of sophisticated chemical
instrumentation to measure the unique properties that
lead to identification.

12. Comparative analysis :
Classification and Individualization
to link a questioned sample and a known
sample to a common originsample to a common origin

13. Class characteristics-
Properties of a substance that are shared by a
group of substances, but are not unique to all
substances of a single origin.
They allow for the placing of a questioned
sample into a class or group of several possiblesample into a class or group of several possible
origins.
For example, a class characteristic of hair is its
color. If a questioned hair sample is brown, it
could be determined that the hair originated from
a person with brown hair.

14. Properties of a substance that are unique
and can be used to establish origin.
For example, if the brown hair sample
contained enough DNA in its root for a
Individual characteristics
contained enough DNA in its root for a
DNA analysis, the DNA would be
considered an individual characteristic

15. Applications of Forensic Chemistry
Drug analysis- deals with the identification of illicit
(illegal) drugs,
Cannabis Sativa
Techniques used
TLC
GC-MS

16. The transfer of trace evidence is governed by what
has become known as the Locard Exchange
The trace analysis
Locard Exchange Principle
has become known as the Locard Exchange
Principle, which states that when two surfaces
come into physical contact there is a mutual
exchange of trace evidence between them.

17. SOIL ANALYSIS
Forensic soil scientists usually obtain soil
samples from crime scenes and suspected control
sites from which soil may have been transported
by shoes, a vehicle, or a shovel.by shoes, a vehicle, or a shovel.
For example, the exchange can take the form of
soil material from a location transferring to the
shoes of a person who walked through that
location.

18. Soil is a complex mixture of both organic and
inorganic material.
1.Microscopic Analysis- The natural variation
of color, texture, general appearance and
presence of vegetative matter are all
recorded.
2.Size Distribution: using a series of sieves

19. 3. Determination of pH:
pH =-log[H3O+]
•Soil pH is commonly determined by forensic
scientists during a soil comparison analysis after
moistening the soil with a predetermined amount ofmoistening the soil with a predetermined amount of
water.
• The pH of the water from the soil is tested using pH
indicators, litmus paper, or a pH meter. Soil pH is a
class characteristic used for comparison.

20. Gunshot residue analysis

21. Gunshot residue analysis
When a firearm is discharged, gases are generated
containing burned and unburned components from both
the propellant and primer of the cartridge. This material
may deposit itself on the clothing of a victim or on the
hands of the person firing the weapon and is referred to as
To determine whether a suspect fired a weapon, a
sample is obtained by tape lifts taken from the hands
of suspected shooters
GSR contains lead,antimony and Barium
Techniquesused-SEM-EDX
gun shot residue.

22. Especially useful in hit-and-run
cases
where the paint chips are analyzed
by FTIR, and SEM. FTIR-used for
comparing the organic binder in the
Paint analysis
Paint transfer on an
paint with that of a standard (for
example, paint from a suspect's
vehicle).
SEM is used for identifying the
constituents of the inorganic
pigments present in the paint.
Paint transfer on an
automobile surface

23. Chemistry is an integral part of forensic science.
Forensic scientists must understand chemistry
principles, concepts, and techniques.
CONCLUSIONS
However, they must also be well versed in all
legal matters relevant to the occupation,
like the criminal justice system, state and
federal laws, and chain of custody.

24. Upon completing an analysis, forensic scientists
must be able to present their findings in a court
of law in a manner understandable to the general
public.
This requires an extensive understanding of
CONCLUSIONS
This requires an extensive understanding of
analysis techniques in addition to the ability to
speak publicly and articulate ideas clearly.
Forensic scientists work neither for the defense
nor for the prosecution; they simply serve as
advocates of the truth under all circumstances.