Development of Latent Fingerp...

Fingerprints have been located on the palm of our hand that are used for the identification of an individual and also used in the forensic field as the main evidence from crime scene.

There are three types types of fingerprints that may be found in a crime scene. Latent (invisible), Patent (visible), and Plastic (3 dimensional impressions).

Patent fingerprints are made by bloods, grease, ink or dirt.

Plastic fingerprints are made by fresh paint, wax, soap.

Latent fingerprints can be made by sweat and oil on skin surface.

Patent and plastic prints seen by naked eyes but for latent you need additional processes for the visibility as they are invisible to naked eyes. Various physical and chemical treatments are used to develop latent prints.

Fingerprint Development Techniques

First, we have to discover and collect prints before choosing the technique to develop the latent prints. The most common methods used for collecting and discovering fingerprints is by dusting a smooth or nonporous surface with fingerprint powder. Before lifting any latent print, we must take photograph of the print.  This is done to avoid any chance of losing latent print during the lifting or retrieval process.

There are several methods or techniques for collecting latent prints: 

Alternate Light Source (ALS)

It is for likely to examine doors, doorknobs, windows, railings etc for investigation. These are laser or LED device that emit a particular wavelength, or spectrum of light. Some device have different filters to provide a variety of spectra that canbe photographed or further processed with powders or dye stains.

Powder Techniques

 a) Brush and Fingerprint powder Development

This is the most common method of developing latent print currently in use. Materials for this are fingerprint powder, fibre glass brush, or camel or squrrel hair brush, lifting tape, latent lift cards and writing implement.

 Methods:

• Apply a small amount of powder to an area with the brush. 
• As a latent pattern becomes visible, the brush strokes follow the print ridge contour. Try to clean the powder from the valleys to make prints clearer.
• The print is then lifted with the tape onto the card or covered with tape and left on the surface of the object. 
• Complete the face of the card with appropriate information. 

 b) Magnetic Powder Development

This technique is generally not good for prints on metal surface or magnetic tapes as the magnet may erase information. Materials used for this method are magnetic wand magnetic particles mixed with powder, lifting tape, latent lift card, writing implement.

Methods: This method is used in a similar fashion as brush and powder. however the magnetic wand should not touch the surface. The magnetic powder is the only part that should be applied to the surface. The magnetic wand may cause scratches on a surface and degrade or contaminate latent prints. 

c) Fluorescent Powder

These powders may be used in the place of powders. These powder tend to be much finer and produce the best result when used with the feather duster rather then the traditional fibre glass. The advantage of this develop the latent prints. The disadvantages is that with the technique additional luminescence is required in the formm of alternate light source to make the print usable. This powder may be just use as traditional powders 

Fuming Techniques

a) Iodine Fuming

Iodine fuming is oldest fuming technique used to develop latent fingerprints.

This technique can be applied on both types of surfaces i.e. porous as well as non- porous. It is successful in developing prints on paper, cardboard, metal and wooden surfaces and also on greasy surfaces.

The development method involves the heating of iodine crystals results directly in the formation of iodine vapors because of the process of sublimation.

The substrate upon which the latent impression is present is exposed to the iodine vapors, a reaction occurred between the fumes of iodine and the sweat components of the print i.e. fatty acids and oily matter. This reaction results in the formation of the yellowish brown colored print. The prints developed by this technique are not permanent or fixed and therefore diminish soon. 

b) Cyanoacrylate / Super Glue Fuming Method

Super glue fuming or cyanoacrylate method is a polycyanoacrylate ester that releases cyanoacrylate esters when it is heated.

It is the method that utilizes the fumes of cyanoacrylate ester (super glue fumes) for the prints development. The technique is suitable for use on a wide variety of non – porous surfaces like rubber, metals, electrical tapes and other such materials and also used to visualize fingerprints inside automobiles. 

In the technique cyanoacrylate fumes react with the trace amino acids, proteins and fatty acids of the fingerprint residue and the print developed are so much firmed and rigid that it is difficult to remove them.

The process is carried out in a chamber or a fuming cabinet fitted with a suitable extraction system.

The article containing the prints is placed in the chamber along with the super glue for up to six hours which discharge fumes of cyanoacrylate ester on heating or these fumes can be created by placing the super glue on an absorbent cotton treated with sodium hydroxide.

This causes the polymerization of the superglue, and the reaction is generally catalyzed by the water content of the fingerprint. 

c) Osmium Tetroxide Method

This is another method employed for the development of prints of recent origin commonly on porous surfaces (like on paper). The solution is applied by making a 1% solution of Osmium tetroxide.

Although, the reagent is more effective in its vapor form rather than the liquid form. Osmium tetroxide works by reacting with the fatty substances present in the perspiration which causes reduction of this reagent from osmium tetroxide to free osmium which is responsible for the color of the print. 

The method involves treatment of the porous surface (paper) with the fumes of osmium tetroxide generated by placing a small amount of reagent in an evaporating dish which is then inturns placed in the fuming chamber for a couple of seconds. 

d) Hydrofluoric Acid

Hydrofluoric acid is the method used for developing the prints on glass. The prints found on the glass due to the oily and waxy components of sweat is detected by the fumes of this reagent. 

e) Mercuric Iodide Method

Mercuric Iodide is the method opted for the development of fingerprints on paper and other allied materials. The method deals with the application of mercuric iodide fumes on the material containing the latent impressions.

f) Ruthenium Tetroxide

Ruthenium Tetroxide (RuO4,) is another fuming method employed for the development of latent fingermarks on a variety of surfaces like on plastic, doors, and human skin and on both porous and non- porous surfaces.

The process make use of the Ruthenium chloride fumes generated chemically by oxidation of ruthenium chloride which is carried out by mixing together a solution 0.1% ruthenium(III) chloride hydrate and 11.3% ceric ammonium nitrate solution at room temperature in a closed container. Any latent marks that come into contact with these fumes are developed over about 10–20 minutes, depending on the substrate. 

Chemical Techniques

Utilizing various chemicals to develop latent fingerprints to allows the investigator the ability to potentially develop prints on any surface if the condition is right.

a) Cyanoacrylate Ester

This technique may be used in two methods, the Fuming or Tenting method, or with the Wand method. CAE react with the amino acids and fatty acids in the pispiration to form a white coloured polymer.

Contrast may be enhanced Through the use of variety of powder or dye stain applied to the developed polymer. Commonly flurocent powders and dye stains are applied on surface where the contrast is less then diserable. 

b) Ninhydrin Method

Ninhydrin is a solution that may be applied by using a spray,seabbing or dipping method. Ninhydrin reacts wih the amino, peptides and protiens contained in the print.

This chemical is used items such as, paper, cardboard, and unfinished wood. This is pinkish or purple colour print of the appears on the item revealing the presence of finger prints. 

To enhance or provide optimal development of ninhydrin prints, the item should be placed in a chamber where the temperature are sufficient. The disered temperature is approxcimately 80 degree F with the humidity rate of approxcimately 80 percent.

c) DFO { 1,8,-Diazafluouren-9-one}/PD [Physical Developer]

Both of these techniques are used on paper or cardboard items. Both techniques are best used through dipping or swabbing the piece of evidence. the evidence should be placed into the chamber where the finger prints allowed to be developed. The reaction is with amino acids, peptides and protiens contained in the prints.

d) Sticky Side Powder /Gentian Violet {Cristal Violet}

These techniques are used on sticky surface. The most common type of surface that these techniques applied to the adhesive tapes. Gentian Violetis used by dipping the iem into bath of the material. sticky side powser mayalso be used in the bath or by painting the adhesive surface. bot techniques involve multistep processing when examining tape. the tape as a shiny side which should be processed for finger print before applying either of these techniques.

Analogue That React With Blood 

Where it is suspected there may be latent fingerprints in the blood, and those prints may not be clearly visible, chemical techniques may be applied to enhance the appearence of fingerprints. The anologs are best used in aerosol form. This means that masks and gloves should be worn to protect the user against unnecessary contamination.

• Leuco-Malachite Green: When sprayed on suspected area, the prints will turn a greenish colour.

• Leuco-Crystal Violet: When sprayed on the suspected area, the prints will turn purplish-black.

• Amido Black/Sudan Black: When sprayed on the suspected area, the prints will turn dark bluish black.

• Luminol: When sprayed on suspected area, the prints will flurosence.

However, there is a chance that fingerprint powders may contaminate or ruin the evidence, depriving investigators with an opportunity to perform other techniques that could highlight hidden print or provide additional information. To avoid such incidents, investigators may also examine the prints with Alternate Light Source or apply Cyanocrylate {super glue} before using powder. 

Like fingerprint powders, chemical processing can reduce the investigators ability to perform other techniques that could reveal valuable information. Therefore, any non destructive investigations are performed before the evidence is treated with chemicals. 

Conclusion

Latent prints are invisible, so it is a challenge for investigators to lift fingerprints. However, there are various methods available to collect latent prints like powder methods and chemical method that make latent prints visible and allows investigators to lift fingerprints and collect a valuable evidence for the court.