Chemicals used in forensic studies

Answer 1

There are four kinds of chemical reagents used to expose invisible, or latent, fingerprints. They

are cyanoacrylate, silver nitrate, iodine, and ninhydrin

Cyanoacrylate

The trade name for cyanoacrylate is super glue.Cyanoacrylate is the active ingredient that makes up 98% of Super Glue. This item has become a very practical and innovative forensic tool. When cyanoacrylate is heated or mixed with sodium hydroxide (NaOH), it releases fumes that interact with the amino acids that are found in the fingerprint residues found on an object, thus making a white print.

Silver Nitrate

Silver nitrate is a chemical ingredient found in black-and-white photographic film. When silver nitrate is applied to a latent fingerprint, the chloride found in fingerprint residue interacts with the silver nitrate and forms another compound called silver chloride. This new compound reveals a black or reddish-brown fingerprint in the presence of ultraviolet light.

Iodine

The third chemical used to reveal latent fingerprints is called iodine. When heated up, crystalline iodine releases iodine fumes into a fuming chamber, where the iodine interacts with the oils found in the latent print thus producing a brownish colored fingerprint. Unfortunately, this kind of print has a tendency to fade rather quickly. Therefore, it must be captured on film right away or fixed by spraying it with a "fixing solution" made of water and starch. This fixing solution allows the print to last for weeks or even months in lieu of a few minutes.

Ninhydrin

The fourth kind of chemical reagent used to reveal latent fingerprints is ninhydrin. Ninhydrin, also known as triketohydrindene hydrate, has been used for many years to reveal latent fingerprints. An object suspected of containing latent fingerprints is sprayed with a solution of ninhydrin. It may take several hours for the fingerprints to show up due to the fact that ninhydrin reacts very slowly with the oils found in the fingerprint. However, heating up the object to a temperature of 80 to 100 degrees Fahrenheit can reduce the reaction time. The resulting fingerprint will be a purple/blue print.

DFO 1,8-Diazafluoren-9-one

DFO is used to develop latent prints on porous surfaces. DFO reacts to the amino acids present in perspiration. The resulting prints will fluoresce with the use of various lasers and light sources. DFO can be either dipped or sprayed. After processing with DFO, the item must be dried and placed in an oven at approximately 100º Celsius (212ºF) for twenty minutes. An iron (no steam) may be used if an oven is unavailable.

Rhodamine 6G

One of the most brilliant dye stains for latent print development on non-porous items with lasers and alternate light sources, after processing with cyanoacrylate. Evident offers Rhodamine 6G as a premixed 1 liter liquid, or in powder form to be mixed with solvent

Crystal Violet

This stain is commonly used for developing latent prints on the adhesive side of virtually all types of tape. A simple solution of crystal violet and water will produce impressive results.

Ardrox Fluorescent Dye Spray

This fluorescent spray is designed for enhancing latent prints that have been developed with cyanoacrylate. It provides excellent ridge details when the latent print is saturated with Ardrox. Prints fluoresce yellow/green. Comes in a 1 liter spray bottle for easy application. Use ultraviolet equipment for viewing results.

MBD Mixture

MBD Mixture is used after cyanoacrylate processing. MBD is fluorescent when exposed to an alternate light source. MBD is offered as a premixed liter

Sudan Black

Sudan Black is one of the best methods for developing fingerprints on greasy or waxy non-porous surfaces such as glass, metal, milk cartons, interiors of gloves, and candles.

Thenoyl Europium Chelate (TEC)

A fluorescent dye used to enhance cyanoacrylate developed latent prints on non-porous surfaces. Visualized most effectively with long-wave UV only. Submerge or flood the item for 2 minutes, then let dry. Expose to long-wave for maximum development.

Basic Yellow 40

This dye is designed to enhance latent fingerprints developed with cyanoacrylate on non-fluorescent, multi-colored surfaces. Prints fluoresce bright yellow/green between 365nm and 485nm with an alternate light source or a UV light. EVIDENT offers Basic Yellow 40 as a premixed liter of liquid.

Basic Red 28

Basic Red 28 is a red dye for use on cyanoacrylate developed prints. After staining with Basic Red 28, a light source or or UV light is used to visualize the prints. Evident offers Basic Red 28 as either a premixed liquid for immediate use, or as a premeasured concentrate to mix with 1 liter of Petroleum Ether or Methanol.

Red-Yellow Mixture

This mixture of both Basic Red 28 and Basic Yellow 40 provides the user with a wide range of fluorescence with cyanoacrylate developed prints. Red-Yellow Mixture is offered as a premixed 1 liter liquid.

RAY Mixture

This mixture of Basic Red 28, Ardrox, and Basic Yellow 40 provides a wide range of fluorescence with cyanoacrylate developed prints. Offered as a premixed liter of liquid.

RAM Mixture

RAM is a fluorescent stain mixture of Rhodamine 6G, Ardrox, and MBD. Use RAM with an alternate light source after processing with cyanoacrylate. Particularly useful in the enhancement of CA developed prints on plastic bags. After processing with cyanoacrylate, RAM may be applied by spraying, dipping, or flooding. Follow with examination under a light source, UV lamp, or laser. Sold as a premixed liter.

Acid Fuchsin

Acid Fuchsin is an excellent stain for enhancing bloody fingerprints or footwear impressions, and has the unique characteristic of fluorescence when viewed under a light source or laser. Bloody latent prints and footwear impressions can be lifted with a white Gelatin lifter, then photographed as is or viewed and photographed under your light source, excited at 515-560nm, and using a red barrier filter (600nm).

Fluorescein

This chemical mixture of Fluorescein causes a catalytic reaction to occur between the hemoglobin in blood, and oxygen. This reaction produces a luminescent stain which will luminesce in the dark when excited with UV or ALS. The major advantage of Fluorescein is that it will continue to luminesce for hours under UV or ALS after the initial application, and without additional applications of the reagent. This product is commonly used to detect blood spatter, blood stained fingerprints and footwear impressions, as well as, blood evidence which has been concealed or cleaned. Fluorescein also reacts with materials other than blood, and therefore caution should be exercised when interpreting luminescent areas.

Zinc Chloride

Zinc Chloride is a traditional method of enhancing prints on porous materials after processing with Ninhydrin. Offered as a 1 liter solution in Methanol.

Nile Red

Nile Red is a lipid stain which reacts to the fats and oils present in a latent print. Nile Red fluoresces with an alternate light source. Apply by spray or brushing onto surface. Available as a premixed liquid, Methanolic or Aqueous.

Phloxine B

Phloxine B is a protein stain which develops a reddish-orange colored print. Phloxine B is particularly good when used to develop latents on dark-colored or multicolored backgrounds. Evident offers Phloxine B as a premixed 1 liter liquid.

Amido Black

Develop faint and often invisible bloody fingerprints and foot impressions with this protein dye stain. Incredible results on most surfaces, even human skin.

LCV - Leuco-Crystal Violet

An effective protein stain used to develop and enhance bloody fingerprints or footprints deposited on non-porous surfaces. Various protein stains, such as amido black, etc., can be used after processing with LCV. Cyanoacrylate fuming may be detrimental to this process. Spraying is the most effective method of application. Use a fine mist, development will occur within 30 seconds. Contains fixative.

Graduated Spray Bottle

Perfect for mixing and applying a variety of liquid based forensic chemicals. Made of durable clear plastic and topped with an industrial grade trigger sprayer. Clearly marked with both ounce and millimeter graduations, as well as, a dilution ratio guide. Works great in the lab or in the field and fits comfortably in the hand. Large 24 oz. size.

Other Chemicals

Blood Enhancement Chemicals,Iron-rich Dust or Soil Impressions,Calcium or Magnesium-rich Impressions