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Introduction

• Although there are many chemical and physical techniques

referred for revealing and enhancing latent fingerprints.• The chemical methods for latent fingerprint detection all

rely on reactions or interactions that occur between theapplied reagent and components of latent fingerprints.

• Studies have shown that the distribution of chemicalconstituents varies widely between individuals, and for thesame individual from day to day and hour to hour.

• The use of techniques in sequence will often thereforereveal more fingerprints than any single technique. Such

sequential processing can be labor intensive and issometimes only used in more serious crime investigations.

• Exhibits from minor crimes will often be treated with onlythe most cost-effective and straightforward process. Thecareful choice of processes and their sequence.



Factors Affecting the Choice of Development

TechniqueThe types of surfaces that are to be treated, it is important that the

following points are considered when selecting a sequence of treatments.

1. The importance of the case and resources available.

2. Techniques should be used if possible in an order in which the

effectiveness of methods used later in the sequence are notadversely affected by those used at the beginning of the

sequence.

3. Any contamination on the surface that could help or hinder

fingerprint development, e.g. blood, grease etc.4. Sampling of biological material prior to treatment for

fingerprints. If this is not possible due to insufficient deposit of

material, specialized advice on the effects of fingerprint

development techniques on DNA profiling should be obtained.



Continue……….

• Samples of other trace evidence such as hairs or

fiber should usually be taken prior to treatment forfingerprints but in a way that does not compromisethe fingerprint evidence. ESDA for developingimpressions in paper must also be performed beforechemical treatments for fingerprint development are

applied.• The effects of exposure to the elements, especially

exposure of the surface to rain or moisture mayaffect the choice of treatment sequence.

• Full use is made of optimized reagent formulationsand specialized equipment at every stage of examination for fingerprints.



1. Samples of other trace evidence such as hairs or

fiber should usually be taken prior to treatment forfingerprints but in a way that does not compromise

the fingerprint evidence. ESDA for developing

impressions in paper must also be performed before

chemical treatments for fingerprint development

are applied.

2. The effects of exposure to the elements, especially

exposure of the surface to rain or moisture may

affect the choice of treatment sequence.

3. Full use is made of optimized reagent formulationsand specialized equipment at every stage of

examination for fingerprints.



Fingerprint Development: Nonporous

Surfaces

• Many articles at scenes of crime fall into this

category including glass, gloss-painted surfaces,

metal and plastic.• Fingerprints on nonporous surfaces can be very

easily damaged as most of the trace residues

deposited from the fingerprint ridges usuallyremain on the surface.



Development techniques



Visual examination

• Visual examination of any article may sometimes

reveal latent fingerprints, particularly if the surface

is smooth and clean.

• A variety of light sources should be used, e.g.

oblique illumination. Any fingerprints should be

photographed before proceeding with other

techniques.



Fluorescence examination • Examination of surfaces with a high intensity light

source or laser, usually working in the near UV, blue orgreen parts of the spectrum.

• Using barrier filters in front of the eyes, will sometimesreveal fingerprints either by the rarely observed

fluorescence of naturally occurring components of thelatent fingerprint, or more often by the fluorescence of some contamination which may have been on thefinger such as oil or grease.

• Fingerprints can also sometimes be visualized by acombination of light absorption by the fingerprintridges and fluorescence of the background.



Vacuum metal deposition (VMD)• The methods that are used to develop latent fingerprints

on non-porous surfaces, this is the most sensitive, beingcapable of detecting monolayers of fat by sequentialdeposition of a very thin coating of thermally evaporatedgold followed by zinc.

• Plastic wrapping materials up to about 1000 mm x 1000mm and other small solid objects may be treated inspecially modified industrial vacuum coating systems.

• VMD has the great advantage that it can develop

fingerprints on surfaces that have previously been wet oreven submerged in water for extended periods of time.

• If fingerprints are not revealed by VMD, superglue, powdersor other techniques may be used subsequently.



Fingerprint powders Powdering • one of the oldest techniques for detecting fingerprints on smooth non-

porous articles, is quite effective and widely used; many latentfingerprints are still found by this simple method.

• Although there are many powders described in the literature, those with aflat, flake like structure such as milled aluminum or brass, or molybdenumdisulfide are significantly more sensitive and generally more effective atdeveloping fingerprints on smooth, clean surfaces than the moretraditional black or white powders which are of a more granular nature.

•The metallic flake powders are most effectively applied with a fine glassfiber brush. Other powders are often applied with soft animal hairbrushes.

• Surfaces which are dirty or contaminated will sometimes take up toomuch of the flake powders all over the surface so that granular black orwhite powders may be more suitable.

• Rough or grained surfaces may sometimes be treated using iron, cobalt ornickel-based powders used with a magnetic applicator although supergluefuming is probably to be preferred.There are many fluorescent powders which may also be used inconjunction with a suitable light source. Powders may be used on surfaceswhich have been wet, but only after the articles have been thoroughlydried at temperatures not exceeding 30°C.



Superglue fuming• Superglue fuming can be used on many nonporous surfaces and is

particularly useful on surfaces such as rough or grained plastic

surfaces which cannot be easily treated using VMD.

• This technique is particularly effective when performed under

optimum controlled conditions (normally 80% relative humidity,

ambient temperature and pressure).

• When superglue fuming is performed under these high humidity

conditions fibrous polymer growth occurs across the ridge deposit

and is believed to be initiated by water droplets present on chloride

deposits in the fingerprint deposit.

• This polymer growth increases mechanical strength and robustnessof the developed fingerprint and produces a very large surface area,

this appears white but can be very effectively enhanced by means

of a solution of fluorescent dye which is absorbed and may be

visualized using fluorescence examination.



Superglue fuming

• Use of fluorescent staining techniques instead of directphotography of the white superglue deposit can doublethe number of fingerprints detected.

• Many dyes have been used but Basic Yellow 40 in ethanolis very effective and is believed to be of lower toxicitythan some others.Superglue fuming may be carried out at reduced pressurebut fingerprints developed under these conditions have asmooth surface with less surface area, are more difficultto visualize and absorb less dye.

Superglue fuming can be used after VMD and powders butis ineffective if used after a water-based developmenttechnique, or on articles that have been wet.



Small particle reagent (SPR)

• SPR consists of a suspension of molybdenum disulfide

suspended in an aqueous detergent solution. • This is used by agitating the reagent mixture so that the

particles are temporarily suspended in the liquid and holdingthe article to be treated under the liquid allowing themolybdenum disulfide particles to deposit onto the surface.

• The article is gently removed and drawn through a containerof clean water.

• The molybdenum disulfide particles adhere to fats depositedin the fingerprint, producing a gray-black image.

• SPR is used in dishes or tanks for portable articles.• SPR can also be used by spraying directly onto larger surfaces,

however used in this fashion it is considerably less sensitivethan the submersion method.



Preferred sequence of techniquesThe order in which techniques are used will be determined

by the following factors:

1. The importance of the case;

2. The size of the article;

3. whether the surface is rough or smooth;4. whether the surface has been wet;

5. surface contamination.When these factors are taken into account, sequences of

treatments can easily be determined.For example, a plastic bag from a serious crime which is notcontaminated with blood etc. might be treated by visualexamination and fluorescence examination followed by VMD

and possibly super-glue fuming or SPR.



Fingerprint Development: PorousSurfaces



Visual examination

Visual examination is less likely to reveal

fingerprints on porous surfaces unless they

have been contaminated with dirt, blood,

grease or similar materials.



Fluorescence examination

• Examination of such surfaces will sometimes detect

fingerprints either by the rarely observed

fluorescence of naturally occurring components of

the latent fingerprint or fluorescence of some

contamination which may have been on the fingersuch as oil or grease.

• Fingerprints can also be visualized on fluorescent

surfaces when the fingerprint deposit absorbs light;again such fingerprints should be photographed

before proceeding.



l,8-Diazafluoren-9-one (DFO)• The most sensitive reagent currently available for detecting

fingerprints on porous surfaces is DFO.• This compound reacts with amino acids deposited in the

fingerprints to produce a faintly colored but intenselyfluorescent compound which can be easily photographed.

• Since amino acids are soluble in water, neither DFO nor

ninhydrin can be used to treat porous surfaces which havebeen wet.

• Articles are dipped into a solution containing DFO,acetic acid and an inert carrier solvent and then heated in a

dry oven at 100°C for 20 min. If humidified conditions areused for DFO-treated articles, no fingerprints are detected.DFO is not routinely used at scenes of crime because it isdifficult to generate sufficient heat in a room to produce anacceptable rate of fingerprint development although localheating can be used for small areas.



Ninhydrin• This is a widely used process which also reacts with amino acids and

produces a purple colored product.

• Articles are dipped into a solution of ninhydrin and acetic acid in an

inert carrier solvent and then heated in a humid atmosphere for rapid

fingerprint development, the optimum conditions are 65% relative

humidity and 80°C for 3-4minutes. (If these same humidification

conditions are used for DFO-treated articles, no fingerprints aredetected.)

• The developed purple-colored fingerprints can be easily recorded

using conventional photography, a green filter can improve contrast.

• Ninhydrin can be very effectively used at scenes of crime with the

same formulation being brushed onto the surfaces. Sealing the

room and raising the temperature with domestic heaters will assist

fingerprint development but development will take several days. The

time taken for this technique varies widely because humidity and



Comparisons

• In large-scale comparisons it has been shown that DFO develops

about 60% more fingerprints than are found using ninhydrin.• However, when ninhydrin is used after DFO, a further 10% of

fingerprints are developed compared to instances where DFO is usedalone.

• DFO is ineffective in developing latent fingerprints if it is used afterninhydrin.

•

When ninhydrin-developed fingerprints are developed on dark non-fluorescent backgrounds or when the background is a very similarcolor to the fingerprint zinc toning can be used to enhancevisualization.

• The fingerprint is treated with zinc chloride solution and gently heatedto produce a fluorescent fingerprint which can then be photographed.

•

Powders Smooth papers may be treated with some types of black ormagnetic powder although these will usually only detect heavier ormore recent fingerprints.

• Superglue fuming This may be used on some smooth surfaces such ascigarette packets but enhancement with fluorescent dyes may bedifficult due to absorption of dye by the background.



Preferred sequence of techniques

• The preferred sequence of fingerprint treatments on poroussurfaces would be: visual examination; fluorescence examination;powders (where applicable); superglue fuming (where applicable);DFO; ninhydrin; physical developer. The actual order to be used in aparticular case will be determined by:

1. The importance of the case;2. whether or not the article has been wet;

3. whether the paper surface is very smooth.If the article has been wet, DFO and ninhydrin are omitted andphysical developer used by itself.

If the paper has a glossy finish, the use of powders or supergluefuming described in the section on non-porous surfaces may be moreappropriate. Good examples of this sort of surface are cigarettepackets and glossy magazines.



Fingerprint Development:Adhesive Surfaces

B k d



Background

Surfaces in this category include the adhesive sides

of sticky tapes and labels. • There are three general techniques that are used

to develop latent fingerprints on these surfaces:

gentian violet, superglue fuming

and powder suspensions.

The gentian violet technique has been used formany years but other techniques are becoming

widely used. Physical developer may also be used

on certain types of paper tapes.

D l t t h i



Development techniques….

Gentian violet (crystal violet) •

The most effective gentian violet formulation (also known as crystal violet)is a solution of crystal violet, phenol and ethanol in water.

• Adhesive tapes are drawn across the surface of the solution two or threetimes so that the dye is absorbed by the fingerprint ridges.

• Other adhesive surfaces to be treated with gentian violet can be floated ontop of, or held in contact with the solution for ease of processing.

• Once treated, the surfaces are washed in slowly running water. Fingerprintson lightly colored surfaces will be visible to the naked eye and can berecorded using conventional photography.

• Fingerprints on black or dark-colored surfaces will not be immediatelyvisible. This problem can be easily overcome by transferring the developed

fingerprints onto photographic paper.• Once this has been done it is important to remember that the fingerprints

will have been laterally reversed. It is important to bear in mind thatfingerprints on the adhesive side of tapes may already be laterally reversedbefore transfer onto photographic paper.



Superglue fuming

• Superglue fuming of adhesive surfaces is

accomplished in the same way as on non-

porous surfaces.

• Again, fluorescent dyeing and subsequent

fluorescent examination may provide

significant enhancement although background

uptake can be a problem.



Powder suspensions• Powder suspensions such as ‘Sticky-side Powder’ can also

be used to develop fingerprints on adhesive tapes. • A concentrated suspension of the powder is applied to the

adhesive side of the tape, either by dipping or carefulbrushing.

• The solution is left in contact with the tape for 10-15 s and

then washed off using slowly running water.• Fingerprints are seen as gray-black images which can be

recorded using conventional photography. Precise treatmenttimes and reagent concentrations have not been determined

or reported to date.Preferred sequence of techniques Little is known about therelative effectiveness of the three techniques above butthe use of powder suspensions or GV will render superglueineffective as an after-treatment as both of the reagents

are water based.



Fingerprint Development: Blood

Contamination



Background

• It is generally advisable that samples of blood are

taken for DNA and other analyses before fingerprinttreatments.

• If this is not possible, specialized advice should besought to determine which fingerprint development

techniques are compatible with DNA profiling; thelatter is a rapidly developing area of technology andcompatibility with fingerprint development techniquesis likely to need reviewing.None of the techniques that are commonly used toenhance bloody fingerprints are specific for blood andtherefore cannot be used as presumptive tests forblood.



Development techniques

Fluorescence examination • An effective method for detecting bloody

fingerprints is by using fluorescence examination toexcite fluorescence of the substrate.

• Blood itself is not fluorescent but absorbs light.Consequently, if the background surface can bemade to fluoresce, the fingerprint can be viewed asblack ridges on a white background.

• Fluorescence examination should be the firsttechnique used to enhance latent fingerprints as itis simple to use and nondestructive provided

significant heating is avoided.



Amido black

• The most commonly used dye for enhancing bloodyfingerprints is Acid Black.

• which is generally referred to as amido black. This is ageneral protein stain which binds to the proteins inblood plasma and to blood corpuscles; amido black is

not a specific blood stain.Amido black is commonly used as a solution inmethanol. However, if a surface has to be treated thatwould be adversely affected by methanol such as

some types of plastic, a water-based formulation maybe substituted.

• Fingerprints developed by amido black are darkblue/black in color and can be recorded using

conventional photography.



• DFO and ninhydrin DFO and ninhydrin can

also be used to develop bloody fingerprints

on porous surfaces. These reagents react with

amino acids in the blood residue to givefluorescent or colored fingerprints,

respectively. As stated in the section on

porous surfaces, DFO must be used beforeninhydrin for fingerprint development to be

effective.



• The most common porous surfaces examined for

fingerprints include paper, wall paper, cardboard

and matt emulsion painted surfaces.

• The reagents used for these surfaces react either

with amino acids, traces of fats and lipids or

chlorides absorbed into the surface.



Physical developer

• (PD) Very little information is available on the

relative effectiveness of this technique for

enhancing bloody fingerprints compared to

amido black, DFO or ninhydrin.

• Powders Powders can also be used to visualize

bloody fingerprints when only part of theridge detail is in blood; carefully applying

powder will develop the ridges which are not

contaminated with blood.



Preferred sequence of techniques

• The preferred sequence for

enhancing bloody fingerprints on

porous surfaces is as follows:fluorescence examination, DFO,

ninhydrin, amido black then physical

developer.



Fingerprint Development: Grease

Contamination



Introduction

• Fingerprints in grease and other types of surface contamination can be enhanced usinga number of techniques such as sudan

black, gentian violet and occasionally physicaldeveloper.

• Other types of contamination can also beexamined using these techniques including

sticky deposits on the outside of drink cansand milk cartons etc.



Sudan black

• Sudan black uses an ethanolic solution of a dye calledSolvent Black to stain the greasy fingerprint ridges.

• The surface under examination is treated with thesolution for 2 min either by immersing the article in the

solution or by floating the article on top of thesolution.

• The surface is then gently rinsed under slowly runningtap water and allowed to dry. Fingerprints are recorded

using conventional photography..



Physical developer and gentian violet

• When enhancing greasy fingerprints on

porous surfaces physical developer can also be

used. On nonporous surfaces, gentian violet

can be used to effectively developfingerprints.

• Little information is available on the relative

effectiveness of either of these techniques

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