Conventional methods of Fingerprint development Presented by:

Farah AroojHassan Abdul Qadir

Presented to:Dr. Zafar Iqbal

Institute of Biochemistry & Biotechnology, University of Punjab.

“Fingerprints found at crime scenes lead to more suspects

and generate more evidence in court than all other forensic

techniques combined.”

Interpol European Expert Group on Fingerprint Identification (IEEFG) Methods for Fingerprint

Identification Part 1 (2004

Introduction

• Friction ridges on hands are known for thousands of years• First suggested by Dr. Henry Flaud in 1880• The use of chemical compounds for the visualization

of latent prints dates back only about 150 years• Most commonly used technique for identification of

criminal.

Types of fingerprints Patent print

Plastic impressions

Latent fingerprint

Patent print

• Visible print by unaided eye. • Example: A good example of a patent printwould be a greasy impression left on a window. • Also in blood, paint, ink, mud or dust

Plastic impressions• These are formed when the raised friction ridges are

physically pushed into the substrate, creating a mold of the friction skin ridge Clay, soft wax, melted plastic,

heavy grease, and paint

Development of patent and plastic prints• Good source of imaging for patent prints• Plastic impressions are usuallyphotographed under oblique lightingthat enhances the contrast of the ridgesand furrows.• These prints may also be preserved with silicone-type casting materials.

Latent fingerprint• The word latent means hidden or unseen. • Latent prints are undetectable until brought out with a physical

or chemical process designed to enhance latent print residue.• Affected by age, gender, stimuli, occupation, disease, and any

substances the subject may have touched prior to deposition.• After deposition: surface area, surface curvature/shape,• surface temperature, humidity, time since they were placed and

temperature.

Biochemistry of latent fingerprint• Help in understanding working of chemicals and

developing new reagents.• A latent print residue is mixture of secretion from glands.• 2 major glands in dermis sebaceous glands and

sudoriferous glands (eccrine and apocrine).• The print is 99% water and rest is trace amount of amino

acids, lipids urea, lactic acid, creatinine, glucose and drugs.

• 250 ng of amino acid per fingerprint. They remain there after water evaporates.

Powders • Finely divided particles that physically adhere to

the aqueous and oily components in latent print residue on nonporous surfaces.

• One of the oldest and most common methods of latent print detection (1891).

• They have affinity for moisture and oily components in a print causes adhesion

2 components.• Pigment (for visualization)• Binder (for adhesion to latent print residue)

(Menzel, 1999, p 143).

• Pigments included lampblack , antimony trisulfide, lead iodide, lead oxide mercuric oxide ,mercuric sulfide

• Adhesive materials included starch, kaolin, rosin, and silica gel

• Available in different colors

VisualizationIs done by reflected/absorbed light or fluorescence

ApplicationBy soft fluffy brush with fine hairs usually made of animal skin. Stiff brushes can damage the latent residue

Carbon black• Consists of charcoal and binder.• Applied on light colored surfaces. EvenShow up on black glossy surfaces as light color• Produce dark gray image• The powder is taken by brush and gently roll on surface. Excess powder is dusted out.The developed fingerprints are preserved On transparent tape.

Advantages• Inexpensive• Covers a large area• Less substrate painting

Disadvantages • Creates mess• Cannot work on porous surface

Magnetic powder Consists of iron powder and pigment A magnetic wand with soft plastic surface is used to pickup the powder and applied The iron filling is then rubbed on surface to deposit the pigment to develop fingerprint.Advantages Easy to clean Can be used on both porous and non-porous

surfaces. Disadvantages Less effective on metal surfaces

WWW.DOWNVIDS.NET-Developing Latent Fingerprints with Magnetic Powder.mp4Video Animation

Aluminum powder• Consists of metal flakes of1-50μm

diameter and 0.5 μm thickness.

• Used on non-porous surface like glass, metallic, highly-varnished surfaces, hard rubber, safes, blue-steel guns or dark-colored surfaces.• Applied by fine fiber glass brush

Fingerprints on car surface

Ninhydrin • First used in 1959 for forensics.• Ninhydrin is used on porous surfaces like paper

and wall.• It reacts with free amines of lysine residue in

proteins sloughed off in fingerprints• Produces deep blue or purple color known as

Ruhemann's purple.• White solid, soluble in ethanol and acetone.

• Applied by spraying or dipping.• Development is done in highly humid environment.

Because water is necessary for this reaction. • Stored in dark place to avoid degradation.Disadvantages• Development need long time without humidity• Storage is difficult because it is degraded after

sometime

WWW.DOWNVIDS.NET-Ninhydrin.mp4

Physical developer• Based on the interaction between lipids and fatty acids of sweat residue

with colloidal silver particles, silver has affinity for them.• Used for developing prints on wet surfaces because Organic residues are

insoluble in water so the physical developer can detect latent impressions • Produce dark gray or black impression• Used on porous surfaces• Used when ninhydrin and iodine fail to work• 4 solutions 1. Maleic acid2. Redox sol (ferrous nitrate)3. Detergent 4. Silver nitrate sol. Fingerprints on cardboard

Steps of developing fingerprint1. Pre acidic wash in maleic acid to remove alkaline

reagents.2. Dip and agitate in working sol. made of ferrous

nitrate, citric acid, detergent, silver nitrate.3. Place the sample under running waterDisadvantages• Time-consuming• Expensive • Destructive• Short shelf life.

Amido black• Used to enhance bloody prints or detect them in

blood• It interacts with proteins in blood and give black

impression• Can be used on both porous and non-porous

surfaces, skin of corpses • Used by mixing with methanol or water.• Rinse the excess dye with distilled water.

Iodine Fuming• Principle: natural body fats and oils in sebaceous

material of a latent print temporarily absorb the iodine vapors. This results in a change in color, from clear to a dark brown, until the effect fades with time

• Iodine fuming is used to reveal prints on porous and semiporous surfaces such as paper, cardboard, and unfinished wood but not on metallic surfaces

• One of earliest methods• Inexpensive and easy• Non-destructive process - other techniques can be

used afterwards

Method• Iodine crystals are placed in

the ceramic or glass dish• Specimen to be processed

is placed in the fuming chamber

• Gently heating the crystals causes them to sublime

• The violet iodine vapor adheres selectively to fingerprint residues, turning them orange

• photographed immediately

• In the lab, iodine fuming is done in a chamber

• On the Crime scene, Fuming wands or fuming guns are used

• These are simple tubes with a small reservoir for iodine crystals.

• The reservoir is heated and iodine vapor is expelled from other end of the tube

Fuming chamber

 iodine fuming gun

• Semi-permanent by treating them with a starch solution, which turns the orange stains blue-black (persist for weeks to months)

• Benzoflavone is another after-treatment for iodine-developed prints. Prints treated with benzoflavone are effectively permanently fixed with a dark blue color. Iodine developed

prints fixed with Benzoflavone (right half)

Starch treatment

Cyanoacrylate Fuming• Also called Super Glue Fuming• Latent fingerprint development ability of

cyanoacrylate discovered in late 1970s.• One of the most frequently-used latent print

development processes.• Used on virtually all nonporous surfaces, including

glass, metal, coated papers, and all forms of plastics

Three Stage Process• Principle: 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.

1. Fumes of Cyanoacrylate (CA) ester monomers are introduced to latent fingerprints and quickly bind with initiators (amines and carboxylic groups) in the residue.

2. The monomer on the fingerprint residue reacts with another CA monomer in the vapor phase to form a dimer on the print. This reacts with another monomer, and another, eventually forming a polymer.

3. The final phase is when the polymer chain reaction is terminated.

Int = Initiator of polymerization. Amines and carboxylic groups in latent print are the primary initiators of Cyanoacrylate polymerization

Method• The object is placed in an

enclosed chamber containing a small electric heater.

• A small tray made from aluminum foil is placed on heater

• When it becomes hot, few mL of cyanoacrylate are added and fuming begins

• Fuming is continued until latent prints develop (30s to 15 mins )

• Can be photographed directly or treated with dyes to increase the visibility and contrast of the prints .

Advantages• Effective on rough surfaces • Vapors are extremely sensitive to fingerprint

residue • Developed impressions are more durable• Adaptable to many different crime scene and

laboratory situations • Relatively cheapLimitations• Liquid CA and its fumes can cause acute damage

to skin, eyes, and mucous membranes • The accumulation of CA fumes on parts of a

firearm could have an unfavorable effect during a subsequent firearms examination

Vacuum Metal Deposition• VMD is a long-established industrial technique for

the application of metal coatings to components such as glass to form a mirror.

• 1968, French workers reported that VMD of a mixture of zinc, antimony, and copper powder was capable of developing latent prints on paper.

• Gold and zinc combination used nowadays• VMD was found to give excellent results on

nonporous substrates

Specimens that have been successfully treated using VMD • Plastic bags and

packaging • Glass and plastic bottles • Firearms. • Glossy card,

photographic paper, and magazine covers

• Clean leather items (including handbags and shoes).

• Adhesive tapes (non-sticky side).

Typical vacuum metal deposition equipment.

Principle• The questioned surface is placed in a chamber from which

the air is evacuated.• The chamber also contains small pieces of gold and zinc

that can be heated electrically to vaporize.• Zinc cannot deposit on the oily residues present in the

fingerprint but gold can deposit on the entire surface.• Gold absorbed into the oil containing ridges of the

fingerprint thus there will be no gold on the surface of the ridges.

Fingerprint Vacuum Metal Deposition.mp4

Continued..• Next, Zinc is

vaporized and will deposit on the substance where Gold is present on the surface i.e. on the background but not on the fingerprint ridges.

• The area where zinc is not deposited will be the fingerprint

Photograph of print developed on Plastic bag by VMD

Advantages• Can develop marks on substrates exposed to

water and conditions of high humidity. • Can safely develop latent prints on firearms• Outperforms all other techniques in developing

prints on plastic bags Limitations• Effectiveness can be reduced by the presence of

body fluids and drug residues.• Difficult to develop prints on heavily plasticized

polymers.• Requires expensive equipment and materials.

Silver Nitrate• Used as early as 1891 for developing latent prints on

porous surfaces.• Useful on paper, cardboard, plastics and

unvarnished, light-colored woodsPrinciple: The silver ions react with the chloride ions in salt contained in the latent print residue to form silver chloride (AgCl), an insoluble salt which turns grey-black when exposed to light

AgNO3 treatment effective because:• The reaction to form the insoluble AgCl is quicker than the ability of the aqueous carrier to dissolve away the soluble NaCl

• Insoluble AgCl gets trapped within the structure.

Continued..• Under room light, the AgCl gradually converts by

photo-reduction to elemental silver of dark grey-black

• Efficient development with 254 nm.• Silver Nitrate solution uses

1-3% w/v aqueous solution for porous surfaces3% w/v ethanol-based solution for water repellant surfaces low absorbency of such surfaces make developed fingerprints fragile

Method1. Spraying or immersion of

surface with silver nitrate solution

2. Rinsed with water after treatment to remove excess silver nitrate

3. The treated surface is exposed to UV light source which reduces AgCl to metallic silver, revealing the prints as gray-black stains

4. The developed prints are photographed immediately and stored in the dark

Latent fingerprints revealed by silver nitrate development

Limitations and AdvantagesLimitations

• In prints older than 1 week, resolution will decrease because chloride ions in the latent print residue diffuse over time

• Latent prints developed by the silver nitrate method on certain types of glossy paper will often disappear within hours

• Used after all other methods because stains of AgCl cannot be removed without destroying the print.

Advantages• Since sodium chloride

is not volatile, very old latent fingerprints retain it and can be developed by silver nitrate so  this can work when other development methods have failed

Methods used by Punjab Forensic Science Agency• Cyanoacrylate Ester• Ninhydrin• Physical Developer• Amido Black

References

• Latent print development by Brian Yamashita and Mike French

• Robert Ramotowski (2013). Evolution of latent print development techniques.

• Processing guide for developing latent print, FBI, USA

Thank you!

Questions?