Methods for iodine and glue fumigation
Overview of part 1 of this series:
Three modern methods used to develop hidden fingerprints:
- Hidden powders for printing: oxide, metallic, combined, fluorescent and magnetic powders
- Chemical development: DFO, nididrin, silver nitrate or a physical developer
- Fuming: a haze of iodine and superglue
1. A hidden fingerprint is one that is usually not visible if it is not processed in any way. The seal itself consists of moisture, mostly water, but also contains a small amount of sweat (sweat) components, such as amino acids, lactic acids, creatinine, choline, sugars, and uric acid.
2. The palms of the hands and soles of the feet are covered with friction combs, and these ridges have sweaty pores along their surface. The sweat of these two areas has one type of sweat gland: Eccrine glands. Of these glands, only water and substances listed above are secreted.
3. Other parts of the body have two other sweat glands: the sebaceous and apocrine glands. The sebaceous glands deplete fatty acids, glycerides and hydrocarbons. In other words, these secretions are oily in nature. The sebaceous glands are associated with hair follicles. Apocrine glands hide water along with ions of sodium, potassium and iron, as well as proteins, carbohydrates and cholesterol.
4. When hands are in contact with the face and hair, they become dirty with this mix.
Iodine-fuming: iodine crystals have a unique characteristic — when exposed to air above room temperature, which begins a process known to scientists as sublimation. This process consists in the fact that solid, like iodine crystals, converge directly in gas iodine vapor. All that is required is some heat to speed up the sublimation process.
Smoke-iodine is a process used to create hidden fingerprints on porous surfaces, such as paper, cardboard, and raw wood. Criminologists and crime scene researchers have discovered that it is a valuable tool for developing hidden fingerprints at a crime scene or in a crime lab. But iodine smoking has several drawbacks.
Iodine fuming
The iodine method of latent print development, as a rule, is the first step in attempts to develop hidden imprints that are considered quite fresh. The advantage of this method is that it does not destroy subsequent testing using other chemicals.
Iodine-haze does not require a complex apparatus to deliver its vapor to a porous surface. Iodine vapor reacts to the secretion of sebum (oil), which contaminate the fingertips. Touch the nose, cheek, ears, hands and chest, and you have these selections on your fingers.
Iodine fumes develop latent prints from orange to brown. This process works best on prints that are known to be fresh; as a ransom note, a deduction note sent to a bank, or even a suicide note.
But, as already mentioned, iodine smoker has its drawbacks — mainly that the prints that appear are runaway — they begin to fade soon after development; and iodine smoke works only on prints that are considered quite fresh. In a minute you will hear more about it.
SPECIAL NOTE: Iodine vapor is toxic. Take all possible precautions.
Smoke removal procedure is extremely simple:
1. Iodine crystals are placed in a confined area with a document or other porous objects. At the crime scene it may be a plastic zippered bag. In a crime lab, this could be a converted fish tank or a smoke chamber that was specially created for this purpose.
2. A low level heat source is used to begin the sublimation process. It may just be your hand wrapped around a zip-top plastic bag containing iodine crystals or an inexpensive coffee preheater.
3. Iodine vapors are usually visible - this is a purple haze. Once the fumes are visible, the heat source can be removed. Printing will be displayed in seconds.
4. The next step is to remove the processed evidence, and then photograph any visible hidden fingerprints. Be sure to include a scale that will be visible in each image. If prints are fresh enough, they should remain visible for 15–20 minutes or longer.
5. After completing the snapshots, you can apply the iodine enhancer / fixative to the designed fingerprints, which provides a permanent image.
Cyanoacrylate smoke:
Back in the late 1970s, an interesting method for developing hidden fingerprints on non-porous surfaces, such as metal, painted wood, plastic, and glass, was shown to employees of the US Army Crime Crime Lab. Instead of using powders, members of the Japanese national police force used a material called cyanoacrylate to develop latent imprints on most non-porous surfaces.
During this period, this material was often called Super Glue. The name Super Glue was a trademark, but with the usual usage, the term superglue became common, and several cyanoacrylate manufacturers used it to describe their product.
If you have ever used it, you know that cyanoacrylate has a very strong, harmful odor. You may have seen an advertisement a long time ago showing how a drop of this glue could tie a car with a hook on a crane that lifted it from the ground. In any case, the glue forms a tight bond, provided that on both surfaces, which must be glued together, there is a very thin film of moisture (water). And, of course, most surfaces on this planet have moisture on them as a result of moisture.
So, how can hidden imprints develop? It is really very simple. A process known as chemical “steaming” is used. Technicians of the criminal laboratory carefully place several pieces of evidence in the application. The early smoking tanks were nothing more than aquariums with a lid of some type.
A few drops of glue are measured in a smoke tray (usually an aluminum cup-shaped object). This is placed in the chamber, and the chamber is closed. Development without any acceleration takes several hours, but when using glue you can use a small coffee preheater to speed up the process.
It is also possible to speed up the smoke removal process by adding a few drops of glue to a cotton swab. To protect the surface of the floor in the smoke chamber, place a cotton swab on a piece of aluminum foil or one of the cups mentioned above. This is one of the serious reasons for NOT wearing cotton gloves. Considerable heat occurs during the firing process and can cause burns in the hands.
Glue vapors will circulate inside the chamber and will come into contact with various points of proof. The vapors will polymerize (turn into a solid) onto any moisture on the remains of fingerprints like objects.
The resulting latent footprints will be as solid as a rock and will correspond to the structure of the ridge that the suspect left. Designed prints have a white color, so visual and photographic contrasts can be added on light surfaces using fingerprints or dyes.
Many crime laboratories have suggested that CSI induces evidence of cyanoacrylate to prevent damage or loss of latent substances during transport to the laboratory.
If you want to learn more about crime investigation techniques, a lot of information can be found on this website.
