Application of chemistry in forensic analysis of Toxicology, Ink Analysis, Fingerprinting.

1. Forensic Analysis of:-
• Toxicology
• Ink
• Fingerprinting

2. Toxicological Studies
 Toxicology refers to the
branch of science
concerned with the nature,
effects, and detection of
poisons.
 It also involves the
measurement and analysis
of potential toxins,
intoxicating or banned
substances, and
prescription medications
present in a person’s body.
 Analytical chemistry which
is linked to toxicology
intrinsically is there fore of
paramount importance in
forensic analysis

3. Why is it important in
forensic analysis?
A police officer pulls over a car for speeding. While proceeding to the car, she
sees the driver hurriedly put a plastic bag in the glove box. Suspecting that the
driver has drugs in the car, she asks the driver to step out of the vehicle. The
officer searches the vehicle and finds the plastic bag with nine other, similar
bags, all containing a white powder. When asked what is in the bags, the
driver responds, “Powdered sugar.” Suspicious that the driver is lying, but
wise
enough not to taste the unknown substance, she retains the bags for analysis
What techniques are available to her to identify the substance quickly and
presumptively on the scene? How can the identity of the substance in the
bags ultimately be confirmed in the crime laboratory?

4. Application in Presumptive
Drug Analysis
 The use of confirmatory analysis
could be time consuming and
expensive making use of
instruments such as gas
chromatogram and mass
spectrometers
 Hence presumptive tests are
performed by forensic analysts in
order to gain insight into the
possible composition of the
substances or the drugs
 Presumptive tests performed in a
forensic lab are mainly of two
types -colour tests and
microcrystalline tests

5. Color Tests
 The sample in question is reacted
with a compound known to produce a
certain colour with the presumed
drug
 If the same colour is formed with the
sample, the drug maybe present in
the sample
 Such tests are generally performed
on small ceramic or plastic plates
with multiple wells called spot plates
 They can not only be performed at a
lab but also by an officer on the site.

6. Some common Drug colour
tests

7. Marquis Test

8. Microcrystalline test
 This test require the
formation of solid
crystals of the sample or
the drug
 The crystals are then
viewed under a
microscope using
transmitted illumination
 These tests are
practically confirmatory
but are complicated
 Identification requires
highly trained experts
 They are not performed
in all forensic labs.

9. Application in measuring BAC(Blood
Alcohol Concentrations)
 The Breathanalyser test
was first invented by
Robert Borkenstein
(1954).
 In the Breathalyzer test,
a subject is asked to
breathe into a container,
whose contents are then
emptied into a chamber
containing potassium
dichromate (K2Cr2O7),
sulfuric acid (H2SO4),
and silver nitrate
(AgNO3).
3CH3OH+AgNO3+2K2Cr2O7+8H2SO4= 2Cr2(SO4)3+K2SO4+3CH3COOH+11H2O

10. An improvement
 Despite the extensive
use of the original
breathalyzer some
errors crept in and had
to be replace
 The modern
breathlysers make use
of spectrometers or fuel
cells to measure the
Blood Alcohol
Concentrations

11. Confirmatory tests
 As the name suggests
these tests provide
conclusive evidence
regarding the presence
of a substance
 They are however more
time consuming and
require use of
techniques such as IR
spectroscopy, Gas
chromatography, Mass
spectrometry etc.

12. Gas chromatography

13. Mass spectrometry

14. Ink analysis in forensic studies
 In forensic studies the
main purpose of ink
analysis is to classify
and compare the
different components
in an ink mixture.
 This is done to make
sure if different parts
of the same document
have been written
with the same writing
instrument or by the
same person.

15. Paper Chromatography-
Simple tool for Ink analysis

16. Forensics
Fingerprinting

17. Dactyloscopy
Principles of Fingerprinting
 A fingerprint is an individual characteristic.
 A fingerprint will remain unchanged during an
individual’s lifetime.
 Fingerprints have general characteristics ridge patterns
that permit them to be systematically classified.
-the study of fingerprints

18. Ridge characteristics for Fingerprint analysis

19. Types of Fingerprint
Visible Plastic Latent
Visible Plastic Latent

20. Lifting Latent Prints
1. Powder Test
• Finely divided particles that physically adhere to the aqueous and oily
components.
• Consists of two components:-
i) pigment- lampblack, lead iodide/oxide, mercury oxide/sulphide
ii)binder- starch, kaolin, rosin, silica gel
• Magnetic powders use magnetism to keep prints intact.
• Atleast 500ng of eccrine solution is required for successful extraction.

21. SPR(Small Particle Reagent) analysis
 also known as the wet powdering method.
 done on plastic, wood, vinyl, glass, metal and cardboard which are
immersed in water for long period of time.
 consists of a suspension of fine molybdenum sulphide particles in an
aqueous medium containing detergent solution (as surfactant).
2. Vacuum Metal Deposition Method
• physical process of coating
evidence with very a thin metal
film under high vacuum.
• are often higher quality with
excellent contrast and ridge
clarity.
• has developed latent
fingerprints on evidence that is
over 20 years old.
• It has also provided remarkable results on exhibits that have been
submerged in water or buried underground.
• This is one of the only available techniques capable of developing
fingerprints on fabrics.

22. Iodine Fuming Chamber
Iodine developed prints(left) fixed with
Benzoflavone(right)
3. Iodine Fuming Method
• Iodine crystals placed in a fume is heated which causes them to sublime
and Iodine vapors adheres to the fingerprint residue turning them
brownish.
• Used on porous and semi porous surfaces.
• In a crime scene iodine fuming guns or wands are used.
• Made permanent by treating with starch solution (turns them blue-black) or
7,8-benzoflavone which turns them dark purple and effectively more
permanent.
7,8-benzoflavone

23. 4. Ninhydrin Reaction
 Triketohydrindene hydrate is the chemical name.
 Proteins are natural polymers containing alpha-amino acid monomers.
 Ninhydrin reacts with α-amino acids and produce a purple-colored
product called, Ruhemann’s purple.
 Although the reaction is relatively slow (24 hours for development), it can
be accelerated by the use of heat or moisture.
 Developing is done in highly humid environment.

24.  Contrast and sensitivity could be further improved by a secondary metal
salt post treatment.
Ruhemann’s purple Ruhemann’s purple metal
ion complex

25. Useful Ninhydrin analogues
1,8-Diazafluoren-9-one (DFO)
• Amino acid sensitive reagent.
• Reaction mechanism is similar to
ninhydrin.
• Yields a highly luminescent
red product .
1,2-indanedione
• Reacts with eccrine
secretions to give a pale
pink color.
• Under treatment with a
strong light source, it
fluoresces with a strong
green light

26. 5. Cyanoacrylate fuming
 Also called Super Glue fuming.
 Latent fingerprint development
ability by cyanoacrylates was
developed in the late 1970s by
Japanese National Police Agency.
 Used on non-porous surfaces like
glass, metal, coated papers and all
forms of plastics.
 Developed impressions are very
durable.

27. • The vapors of Cyanoacrylate are selectively attracted to fingerprint
residues, where it builds up as a crystalline white deposit that can be
photographed or copied onto tape strips.
• The monomer form of cyanoacrylate is vaporized and polymerizes and
binds selectively with initiators(water, amines and carboxylic acids)
on a fingermark residue.
• The formationof polymerized cyanoacrylate enables visualization of
ridge detail whilst protecting the fingermark from smearing and
degradation.
• The application of heat, vacuum chamber is widely used to accelerate
the fuming process where higher humidity levels result in better,
more visible ridge detail.
PRINCIPLE

28. Method of Analysis
• The object is placed in an enclosed
chamber containing a small electric
heater.
• A small tray made from aluminium foil is
made which is placed on heater.
• When it becomes hot, few mL of
cyanoacrylate are added and fuming
begins.
• Fuming takes place for about 30mins-1hr
for latent prints to develop.
• Can be photographed directly or some
fluorescent dyes like Rhodamine 6G is
used to further enhance the visibility and
contrast of the prints.

29. References
• FORENSIC CHEMISTRY David Collins Brigham Young University—
Idaho.
• Forensic Chemistry- the new chemistry by David E. Newton.
• https://www.compoundchem.com/2016/07/26/fingerprints/
• https://cen.acs.org/analytical-chemistry/forensic-science/Fingerprints-
just-patterns-re-chemical/97/i10
• Forensic Chemistry Fundamentals and Applications by Jay A.Siegel

30. “Once you eliminate the impossible, whatever remains,
no matter how improbable, must be the truth”
Thank You