Latent Fingerprint Recovery and Amplification Unit Two Forensic Science Notes 2.4

In the human population: Whorls (27.9%) Loops (33.8%) Arches (38.3%) Of the arches: 31.7% of human prints are plain arches; only 6.6% of prints are tented arches

Fingerprint Types Fingerprints found at a crime scene fall into three categories Patent Plastic Latent

Patent Fingerprints Patent fingerprints are those that are readily seen and are transferred from the friction ridges by a foreign substance, like blood, oil, paint or dirt.

Plastic Fingerprints Plastic fingerprints are prints that are impressed into a soft substance such as wet paint, putty or wax.

Latent Fingerprints The latent fingerprints are those left behind by the natural body secretions, such as perspirations, or oils and acids. They are not readily visible.

Fingerprint Recovery There are many techniques and methods in recovering fingerprints such as the use of different powders, light sources, sprays and photographic filters

Fingerprint Powders Various dusting powders can be used depending on the type of surface to be examined carbon black powder on light surfaces lanconide for prints on dark surfaces aluminum powder can be used on either type Remove the excess powder by blowing the dust from the surface or by gently brushing it away. If a camera is available, try to photograph the print. Lift the print from the surface with tape

Fingerprint Amplification There are many techniques and methods in recovering fingerprints such as the use of different chemical agents: ninhydrin, cyanoacrylate, and iodine fuming.

Konai's hand print was impressed on the back of the contract. , . Ninhydrin Konai's hand print was impressed on the back of the contract. , . Ninhydrin bonds to the amino acids in the fingerprint. used on porous and non-porous surfaces purple-colored prints permanent The Acetone that carries the ninhydrin is harmful to the respiratory system (so don’t inhale!)

Iodine Solid iodine crystals give off vapors that bond physically to the oily substances of a fingerprint. used on porous and non-porous surfaces brown-colored prints not permanent unless fixed works best on fresh prints Iodine fumes are toxic and also strongly corrosive.

Cyanoacrylate Cyanoacrylate interacts with a latent fingerprint. Super Glue is 98 to 99 percent cyanoacrylate ester The fumes and the suspect material are placed in an enclosed chamber for up to 6 hours. can be mixed with sodium hydroxide can be heated gently The cyanoacrylate bonds to the prints leaving a white residue