CONTENTS

1. Introduction

2. Can your fingerprints be changed or stolen?

3. How long do fingerprints last?

4. Pattern of fingerprints and fingerprint characters

5. What is a Latent Fingerprint?

6. Constituents of sweat

7. Chemical techniques of fingerprinting

7.1 Ninhydrin Reagent

7.2 Iodine Fuming

7.3 Iodocamphor

7.4 Cyanoacrylate Fuming Method

7.5 Silver Nitrate

7.6 Eosin-blue dye and Erythrosin-B dye

7.7 Rose Bengal

7.8 Triazine Reagent

7.9 Small Particle Reagent Formation

7.10 Nanoparticles

8. Experiments performed

8.1 Experiment 1

8.2 Experiment 2

8.3 Experiment 3

9. Conclusion

10. Bibliography

APPLICATIONS OF CHEMISTRY IN

FINGERPRINTING

1. Introduction

A woman has been murdered. When the detectives arrive on the scene, the house is in shambles.

Clothes are strewn about the floor, lamps are overturned and thers no sign of the assailant.

Then one of the detectives picks up a glass. On its side is a smudged , bloody thumbprint. He

takes it down to the lab, where its analysed and matched to a recorded set of prints. The

detectives catch their killer.

This scene has been replayed in one crime drama after another. Ever since scientists discovered

that every person‟s fingerprints are unique, and police officers realized this singularity could

help them catch criminals, fingerprints have been an integral part of the law enforcement

process. Today, fingerprints are also used to prevent forged signatures, identify accident victims,

verify job applicants and provide personalized access to everything from ATMs to computer

networks.

But fingerprinting has come a long way from the days when police officers lifted prints from a

crime scene and checked them manually against their files. Modern fingerprinting techniques

can not only check millions of criminal records simultaneously, but can also match faces,

backgrounds and other identifiable characterstics to each perpetrator.

Our fingerprints give our fingers the rough surface we need to create the friction that allows us

to pick up a baseball or hold onto a pencil to take a test. They are 100% unique – no two

people have the exact fingerprint.

2. Can your fingerprints be changed or stolen?

A minor scrape, scratch or even burn won‟t affect the structure of the ridges in your fingerprints –

new skin reforms in its original pattern as it grows over the wound. But each ridge is also

connected to the inner skin by small projections called papillae. If these papillae are

damaged, the ridges are wiped out and the fingerprint destroyed.

Some criminals have tried to evade capture by tampering with their own fingerprints. Chicago

bank robber John Dillinger reportedly burned his fingerprints with acid in the 1930s. recently, a

man in Lawrence, Mass., tried to hide hids identity by cutting and stitching up all ten of his

fingertips (fortunately, a police officer recognized his face).

But as fingerprint technology becomes a common form of authentication from bank vaults to

luxury cars, law enforcement officials worry that would-be criminals might try to steal entire

fingers for the prints. In one case, robbers in Malaysia cut off a man‟s fingers so they could

steal his Mercedes. Companies that make biometric security realize the potential dangers of this

system, and are now creating scanners that detect blood flow to make sure the finger is still

alive.

3. How long do fingerprints last?

Fingerprints can last for years on an object if it is not cleaned after being touched. This can be

observed easily on an old silver.

4. Patterns of fingerprints and fingerprint characters

Fingers have ridges. Ridges give prints. Ridges are always not parallel. The fingerprint character

modifications are such as- Ridge

Termination, Island, Hook, Bifurcation, etc.

7.11 Powder Method

The application of finely divided materials and the subsequent removal of the excess powder by

brushing, blowing or tapping has been the universal method of intensifying fingerprints on non-

absorbent surfaces since the early days of fingerprint technology. The technique relies on the

mechanical adherence of fingerprint powder to the moisture and oily components of skin ridge

deposits.

Acts on – Water

Fixing Agent – Silica/Charcoal (Charcoal – colourant, Silica – adhesive)

8. Experiments performed

8.1 Experiment 1

Aim – To detect fingerprints by conventional powder method and to match the prints with a

fingerprint record chart. To investigate its advantages and disadvantages.

Materials Required – Talcum powder, Manganese Dioxide, blender, brush, variety of surfaces

Experiment –

1. Weigh out 3 grams of either of the following: Talcum powder, chalk powder or starch, or a

mixture of these.

2. Mix it with 1 gram of charcoal or Manganese dioxide.

3. Use a mixie to thoroughly mix these components.

4. Put a latent print on an item: paper, glossy paper, lamination sheet, utensil, etc. Put some

powder on the print and lightly spread it with a paint brush.

5. Blow off excess powder.

6. Prepare 2 compositions and compare the results.

Advantages – Works on a variety of surfaces. Cost effective.

Disadvantages – Not applicable to lod prints

Precautions – Do not put excess powder

Conclusion – The method works well on lamination sheets, transparent covers, glossy sheets,

steel items, etc. But it does not work on old prints.

8.2 Experiment 2

Aim – To carry out Iodine Fuming technique. To investigate its advantages and disadvantages.

Materials Required – Iodine crystals, starch, container, water bath, paper specimens.

Experiment –

1. Choose a fuming chamber (kitchen container) about the size of your specimen.

2. Sprinkle a few pieces of iodine in it.

3. Place the specimen in the chamber.

4. Cover the chamber with a lid.

5. Apply heat on the container.

6. Take out the specimen 5-10 mins and sprinkle starch solution on it.

Observations – Violet Iodine vapours fill the chamber. The specimen has dark brown

fingerprints. On applying starch solution, prints turn blue black in colour.

Conclusion – I found that iodine fuming was a really effective method on semiporous

materials like glossy cardboard, etc and paper where fuming with super glue or Ninhydrin

treatment doesn‟t work. Best used for porous surfaces such as paper.

Advantages – Simple, cost effective, non destructive, reversible.

Disadvantages – Iodine is volatile, the prints evaporate in a matter of hours/days. I had to

apply starch to fix them to make them last longer.

Precautions – Cover your work surface with newspapers as iodine stains anything it comes in

contact with.

8.3 Experiment 3

Aim – To carry out the Super Glue Fuming technique.

Materials Requires – Super Glue, Sodium Hydroxide, container, glass slide, water

Experiment –

1. Choose a fuming chamber (kitchen container) the size of your specimen.

2. Put a paper in it and put some water in it to provide humidity.

3. Make a small aluminium foil boat to contain the super glue and place that in the fuming

chamber.

4. Put a microscope slide in the container.

5. Put a drop or two of super glue on a pad.

6. Put a drop or two of 0.5 molar Sodium Hydroxide to accelerate the process.

7. Take out the specimen after 5-10 minutes.

Observations – Fingerprints are developed as white crystalline traces.

Conclusion – I found that Super Glue Fuming was a really effective method on non porous

materials like glassware, plastics, metalware, etc.

Advantages – Simple, cost effective.

9. Conclusion – Application of chemistry to fingerprinting

The Principles of Chemistry have been used for the benefit of mankind – medicines, synthetic

fibres, soap, detergents, bleaches, pastes, explosives, fuels, etc. Chemistry has influenced our

lives so much that we don‟t realize that we come across chemicals at every moment.

Fingerprinting, which is a part of forensic science, shows extensive use of chemistry. Many dyes

are used to study and detect constituents of sweat in fingerprints. Different chemicals are used

to detect fingerprints in different media. Eg – Ninhydrin is a fixative agent. Rose Bengal,

Iodcamphor, cyanoacrylate, etc. are chemicals used in fingerprint study.

“Lots and lots of processes take advantage of the chemistry of fingerprints”, says Robert Shaler,

professor of biochemistry and molecular biology and director of Penn State‟s Forensic Sciences

Program.

BIBLIOGRAPHY

1. Journals by Prof. GS Sodhi, SGTB College, DU

2. Wikipedia, the free Encyclopedia

3. How Stuff Works website

4. FBI, Recording Legible Fingerprints

5. Onin.com

6. ochemonline.wordpress.com

7. leefofland.com

8. Bombay Hospital Journal

9. NCBI, Pub Med

10. Egyptian Journal of Forensic Sciences

11. youtube.com

Aim of the investigatory project

- To carry out a scientific investigation involving laboratory testing and collecting

information from other sources on Application of Chemistry in Fingerprinting.

- To investigate various chemical techniques of fingerprinting.

- To carry out fingerprinting exercise using powder method on a variety of media.

- To perform techniques like Iodine Fuming and Super Glue Fuming in the laboratory.

ACKNOWLEDGEMENT

“A good teacher is like a candle – it consumes itself to light the way for

others.”

A big thanks to Tina Pratap Ma’am for her incessant support and

encouragement. Ma’am is very helpful and has always been there for her help,

support and always kept my spirits high.

I would also like to express my gratitude for our Chemistry Lab Assistant – Mr.

Dinesh Sir. He has always allowed to work in the lab and he was always there to

help.

Big thanks to our Principal Ma’am, Mrs. Geeta Parashar for being encouraging

and supporting.

Digvijay Das

XII-A

An average fingerprint has 85 such characters (island, hook, bifurcation, etc.). Its interesting to

note that not all fingers on a given hand will bear the same pattern.

In fingerprinting we compare position of fingerprint characters ( island, loop, hook, ridge

pattern, etc.). According to Indian Law at least 8 characters should be same and at the same

position. 1/10th of finger‟s print is enough to detect crime.

5. What is a latent fingerprint?

The term „latent‟, in the context of fingerprint work, simply means „invisible‟. Many impressions

are composed of a thin film of natural secretion and/or foreign material in such a small

quantity that they are invisible without some form of enhancement. A latent fingerprint is form

when the sweat pores of the papillary ridges leave a deposit of perspiration on a surface with

which the finger has been brought into contact.

6. Constituents of sweat

Water – 99%

Inorganic ions – 0.5% (eg. Pottasium, Magnesium, Sulphate, Calcium)

Organic compounds – 0.5% (eg. Amino acids, Fatty acids, Ammonia and Urea)

7. Chemical techniques of fingerprinting

Various chemical reagents, such as, silver nitrate, iodine and ninhydrin are available for

rendering visibility to latent prints. These reagents react with sodium chloride, fatty acid and

amino acid contents, respectively, present in the sweat. The powder technique of developing the

latent prints is the most common and most widely used.

7.1 Ninhydrin Reagent

Ninhydrin (2,2-Dihydroxyindane-1,3-dione) is a chemical used to detect ammonia or primary and

secondary amines. When reacting with these free amines, a deep blue or purple colour known as

Ruhemann‟s purple is produced. Ninhydrin is most commonly used to detect fingerprints, as the

terminal amines of lysine residues in peptides and proteins sloughed off in fingerprints react

with ninhydrin.

Advantage – Ninhydrin reagent may be used for developing prints as old as 15 years.

Disadvantages – However the disadvantage of this technique is that ninhydrin has to be

dissolved in an organic medium. Since nowadays oil bases inks are most often used, spraying an

organic solvent on a document may despoil the calligraphic script. Further ninhydrin gives a

background reaction with melamine coated currency notes and its use is therefore precluded.

7.2 Iodine Fuming

The iodine fuming technique has historically been recognized as one of the earliest techniques

available to the investigator for developing latent prints.

Advantages –

1. The iodine fuming is essentially a non-destructive technique.

2. Iodine fumes are sensitive to different latent residues than other methods.

3. Cost effective.

Disadvantages – The prints obtained by iodine fuming are not permanent and tend to fade out

with time, unless fixed. The toxicity of iodine also limits the use of this method.

7.3 Iodocamphor Method

Camphor + Iodine → 2-Iodocamphor

It is a modified method of iodine fuming in which the coloured prints do not evaporate.

Advantages – Can be used to detect fingerprints having SOOT on them.

7.4 Cyanoacrylate Fuming Method

The cyanoacrylate fuming method (often called as the super glue fuming method) of

developing latent fingerprints has proven to be an effective tool for professional investigators

and the quality of its results has made it a popular one.

Most liquid super glues are really either methylcyanoacrylate or ethylcyanoacrylate. Less

common types of super glue include butylcyanoacrylate and isobutylcyanoacrylate.

Fortunately, all these types of super glues are nearly identical physically and chemically.

Super glue reacts with the traces of amino acids, fatty acids and proteins in the latent

fingerprint and the moisture in the air to produce a visible, sticky white material that forms

along the ridges of the fingerprints. The final result is an image of the entire latent fingerprint.

This image can be photographed directly or after further enhancement.

To enable such a reaction to take place, the cyanoacrylate must be in its gaseous form. If any

latent fingerprints exist anywhere inside the tank, they will eventually be exposed to the

gaseous cyanoacrylate.

Advantages – The super glue technique produces outstanding results on all non-porous surfaces

like metal, glass and plastic.

7.5 Silver Nitrate

Silver nitrate has been used to reveal fingerprints on non-porous materials and paper. The

effectiveness of silver nitrate results from its reaction with chlorides present in sweat by forming

silver chloride which rapidly turns black on exposure to light.

7.6 Eosin-blue dye and Erythrosin-B dye

Technique – Two formulations based, respectively, on eosin-blue dye and erythrosine-B dye,

have been prepared for detecting latent fingerprints. Calcium content of sweat is fixed with the

help of a phase transfer catalyst. The formulations use cheap, insoluble, salts as adhesive

materials in place of costly, resinous polymers, which most conventional powders incorporate.

Advantage – The formulations are non-toxic and cost-effective. They can develop fingerprints on

a wide range of surfaces by fixing the inorganic ions and proteins of the human sweat deposit.

These reagents offered many advantages. They are absolute non-toxic and are used in cosmetics

and as dyes. They are fluorescent in nature and therefore, can detect weak prints under

ultraviolet light. Moreover, they are known to form coloured complexes with inorganic proteins

and proteins present in human sweat. Latent fingerprints developed by using the aforementioned

two formulations are sharp, clear and visible to the naked eye. They persist over prolonged

periods of time.

Advantage – Eosin-blue is a non toxic fluorescent dye.

7.7 Rose Bengal

Rose Bengal (4,5,6,7-Tetrachloro-2‟,4‟,5‟,7‟-tetraiodofluorescein) is a stain. It is an anylatical

reagent. It is a phase transfer catalyst. It is a t-Tetrabutylammonium iodide. It can work on

calcium ions. It is used for laminated surfaces, adhesive tapes, duct tapes, etc.

7.8 Triazine Reagent

Triazine Reagent is Iron-(pyridyliphenyltriazine) complex. If you hold any substance made of

iron, small nanoparticles of iron dissolve in our sweat. When triazine reagent is sprinkled red

colouration is obtained.

7.9 Small Particle Reagent Formulation

A suspension of Eosin Y coated on ZnCO3 in a detergent solution may be used as a Small

Particle Reagent on metallic surfaces.

Advantages – Safe, simple and not costly.

7.10 Nanoparticles

Criminal investigations may benefit from new forensic methods based on nanoparticles. A

technique using gold nanoparticles in combination with antibodies has shown promising results

for enhancing fingerprints that are over a week old. Nanoparticles have excellent adsorption

power. Nanoparticles of Alumina are also used.

Xanthe Spindler at the University of Technology Sydney in Australia and colleagues now report

a technique that targets amino acids – present ubiquitously in sweat and thus in most

fingerprints. They linked amino acid-binding antibodies to gold nanoparticles and applied them

to fingerprints. To develop and image the prints, they used red flouroscent secondary antibodies

that would stick to the nanoparticle-bound antibodies.

Antibodies bound to nanoparticles can bind to amino acids in fingerprints that are over 12

months old.

Advantages – They give sharp detail and we get lots of antibodies across the surface of the

fingerprint, which then when we put the dye on would mean a much higher dye response.

Disadvantage – The new nanoparticle-based method performed well for prints made more than

a week previously. However, conventional fingerprint enhancing techniques still work better for

fresh prints.

CERTIFICATE

This is to certify that Digvijay Das of class xii-B, Roll no. 9,

Modern Convent School, has successfully completed his

investigatory project on Applications of Chemistry in

Fingerprinting, in the academic session 2012-2013.

Tina Pratap

PGT, Chemistry

Modern Convent School