| You have seen it on your favorite CSI TV program | | | | close proximity of the latent prints, allowing the |
| when the police scientist uses gaseous fumes to | | | | technician to fix and dye the fingerprint |
| expose fingerprints found at a crime scene. Have you | | | | simultaneously. |
| ever wondered what those fumes are? Have you | | | | Silver nitrate is a chemical ingredient found in |
| ever heard of terms like "Super Glue" mentioned by | | | | black-and-white photographic film. When CSI |
| the characters on CSI? | | | | technicians apply silver nitrate to a latent fingerprint, |
| In this article, I will discuss the various kinds of | | | | the chloride found in fingerprint residue interacts with |
| laboratory chemicals that are used to reveal invisible | | | | the silver nitrate and forms another compound called |
| fingerprints. | | | | silver chloride. This new compound reveals a black or |
| In many crime labs, there are four kinds of chemical | | | | reddish-brown fingerprint in the presence of |
| reagents used to expose invisible, or latent, | | | | ultraviolet light. |
| fingerprints. They are cyanoacrylate, silver nitrate, | | | | The third chemical used to reveal latent fingerprints is |
| iodine, and ninhydrin. | | | | called iodine. When heated up, crystalline iodine |
| What is cyanoacrylate? Perhaps you know this item | | | | releases iodine fumes into a fuming chamber, where |
| by its trade name, Super Glue. It is this same Super | | | | the iodine interacts with the oils found in the latent |
| Glue that you can purchase at any Home Depot or | | | | print thus producing a brownish colored fingerprint. |
| Walmart. Cyanoacrylate is the active ingredient that | | | | Unfortunately, this kind of print has a tendency to |
| makes up 98% of Super Glue. This item has become | | | | fade rather quickly. Therefore, it must be captured |
| a very practical and innovative forensic tool. When | | | | on film right away or fixed by spraying it with a |
| cyanoacrylate is heated or mixed with sodium | | | | "fixing solution" made of water and starch. This fixing |
| hydroxide (NaOH), it releases fumes that interact | | | | solution allows the print to last for weeks or even |
| with the amino acids that are found in the fingerprint | | | | months in lieu of a few minutes. |
| residues found on an object, thus making a white | | | | The fourth kind of chemical reagent used to reveal |
| print. | | | | latent fingerprints is ninhydrin. Ninhydrin, also known |
| After exposure to cyanoacrylate, the fingerprints can | | | | as triketohydrindene hydrate, has been used for |
| then be captured on film as is or treated with a | | | | many years by CSI technicians to reveal latent |
| fluorescent pigment that sticks to the fingerprint. The | | | | fingerprints. An object suspected of containing latent |
| fingerprint then fluoresces, or glows, under a laser or | | | | fingerprints is sprayed with a solution of ninhydrin. It |
| ultraviolet light source. | | | | may take several hours for the fingerprints to show |
| An object that is suspected to have latent | | | | up due to the fact that ninhydrin reacts very slowly |
| fingerprints in this method many times is exposed to | | | | with the oils found in the fingerprint. However, |
| the fumes inside a gadget called a fuming chamber. | | | | heating up the object to a temperature of 80 to 100 |
| The end result is that the fumed fingerprints are now | | | | degrees Fahrenheit can reduce the reaction time. The |
| hard and stable as one would expect from Super | | | | resulting fingerprint will be a purple/blue print. |
| Glue. In place of setting up a fuming chamber at the | | | | Hopefully, you have been educated on the kinds of |
| scene of a crime, CSI technicians often times use a | | | | chemicals used on your favorite CSI show. The next |
| hand held wand-shaped tool that heats up a small | | | | time you hear any of these chemical tools used on |
| cartridge of cyanoacrylate mixed together with | | | | TV, you will know exactly what they are talking |
| fluorescent pigment. This tool then releases gases in | | | | about. |