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Iodine fuming Method for Latent Fingerprints May 09, 2022 - BY RealScan Biometrics

Iodine fuming Method for Latent Fingerprints

Iodine fuming is one of the earliest forensic techniques for detecting latent fingerprints, as well as one of the most straightforward techniques.

In this invisible fingerprints on a piece of white paper are produced by fuming iodine crystals that can be found at any science supply store or school lab.

Iodine crystals give out vapor’s (sublimation) that attach physically to the oily substances of a fingerprint during development.

The iodine-developed brown prints are not permanent until they are repaired.

Benzoflavone darkens and fixes the print.

Both porous and non-porous surfaces can be treated with iodine fuming. It's great for new prints (usually no more than a few days old).

Iodine vapors are poisonous and highly corrosive. Other procedures can be employed after the iodine fuming approach because it is non-destructive in concept.

Crime Scene Fingerprint Analysis

Fingerprints are one of the most fundamental methods used by forensic experts while gathering evidence at a crime scene.

A variety of chemical and physical processes can be used to create fingerprints.

The identification and visualization of latent fingermarks is a crucial part of a scientific investigation of a crime scene.

The most popular methods of latent mark production have been powder dusting, ninhydrin, iodine fuming, and silver nitrate soaking.

One of the oldest known procedures for the production of latent fingermarks is iodine fuming.

Sublimation produces violet iodine vapor when iodine crystals are heated. Iodine fumes bind to fingerprint residues (sebaceous material) on the latent finger mark deposit, resulting in yellowish brown latent prints.

The technique is easy, quick, efficient, and cost-effective, and it may be used on a variety of porous and nonporous surfaces (including paper, wood, plastic, and glass).

Iodine sterilization has always been recognized as one of the first techniques available to researchers to develop latent prints.

Before the advent of chemical methods such as ninhydrin, iodine fumigation was a preferred and recommended method for use on paper products. Although frequently placed under "chemical engineering" the development of latent prints with iodine vapor is not a chemical action but a physical one.

Chemical reactions are those where the application of a chemical alters the physical properties of the latent residue e.g. ninhydrin interacts with the physical quality of the amino acids in the latent residue.

However, in iodized smoke the body’s natural fats and oils are present in the slime of a latent imprint that temporarily absorbs iodine vapor.

This results in a color shift from light to dark brown until the effect fades over time.

Color shifts can be made permanent y applying certain materials but latent growth can often be photographed at the greatest intensity of color change and then allowed to fade.

Impressive immobilization of iodine with other applications may prevent further processing of other chemical and physical means.

The transient nature of the latent substances developed by iodine which requires immobilizers to the exclusion of other processing techniques may lead to a low use of this method.

The reversible addition of iodine to the double bonds of unsaturated fatty acids in fingerprint residue by the process of halogenations was initially thought to be the mechanism of the iodine fuming reaction.

However, physical adsorption rather than a chemical reaction was suggested as the mechanism of interaction. Latent fingermarks created with iodine vapors are difficult to photograph because they vanish in a short period of time due to sublimation.

As a result, fingermarks may necessitate iodine re fuming. Some of these methods include post treatment of iodine impressions with starch steam or water benzoflavones.

All of these reported methods have their own limitations in terms of background contrast the  being only applicable to a specific type of surface the  and the short viewing time of fixed fingerprints thus making lost probability value  when deleting fingerprint details.

To perform the experiment people choose porous and non-porous substrates.

Porous substrates include a variety of commonly used papers (plain paper, bonding paper, marker paper and non-porous surfaces (high- and low-density polyethylene) plastic sheets aluminum foil glass).

Latent fingerprints of the same individuals were collected on these substrates under ambient conditions.

It is mainly used in porous and non-porous surfaces and unfinished wooden surfaces.

Also it reacts with fatty acids and oily matter to visualize friction ridge in detail and also it’s a non-destructive technique, in maximum yellow brown details is developed upon exposure to iodine fumes.

The developed ridge disappears quickly so it is necessary to take photographs quickly the developed prints.

Iodine vapor is sensitive to potential residues differently than other methods. It is possible that the latent prints produced by iodine vapor were not grown by other means the application of which would then destroy the residue required for iodine growth.

Iodine Fuming in Criminal Investigations

When the nature of the surface matters regarding a particular technique or sequence iodization must certainly be considered.

This has been the case for a number of years involving a surgical bandage.

White surgical bandages were used to tie up a victim in a sexual assault. The victim eventually freed herself and tore the tape.

A tape was recovered from the water in the toilet owl where it had been lying still.

The strip was sent to a la for testing. That was before the development of special adhesive powders.

It was decided to use an iodinated sterilization device on the adhesive side of the surgical tape. An excellent fingerprint almost like a "rolled up" fingerprint is developed photographed and then identified on the attackers left thumb.

The original techniques may be old but still viable. All techniques should be considered in their appropriate order in an effort to locate and recover potentially investigative useful prints.

Developing Latent Prints With Iodine

When your finger presses on the paper, the oil from the skin is transferred to the paper. These oils then react with the iodized vapor producing a brown color with traces of fingerprints.

The fingerprints developed in this operation are called latent fingerprints because they are initially invisible to the naked eye.

Latent fingerprints must be developed by chemical or physical methods.

Visible fingerprints are fingerprints that are visible to the naked eye such as traces of ink paint or blood.

Latent fingerprints don’t last forever as they can smudge erase or wash off the surface. They can also disappear when the substance that forms the fingerprints evaporates into the air. Children’s fingerprints fade much faster than adult fingerprints especially in hot weather.

This is due to the difference in the composition of the oils on the skin of children compared with that of adults which is thought to change during puberty.

Before puberty finger oils mainly contain small fairly volatile fatty acids with about 13 carbon atoms.

After puberty the composition of these oils in the fingers contains Alkyl esters which are larger and less volatile with about 32 carbons.

These larger esters may not be secreted by fingers but rather y the sebaceous glands of the face. They are then transferred to the fingers by touching the face.

Because children’s fingerprints contain more volatile components they evaporate faster. This makes sense when children are involved in a crime as their fingerprints can fade when police arrive at the scene to rush them off.

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