Question

Consider the following list of evidence to be processed for latent fingerprints.   Please write a paper detailing how you would process and recover the latent prints from the items. Clearly explain: 1) why you chose these methods rather than other means of processing and, 2) if the methods you chose would be different if you were operating in the field versus working in a controlled laboratory environment and why.

A plastic bag

Answer 1

• Latent prints are the most common type of print and take the most effort to locate since they are invisible. Latent prints occur when someone touches any porous or nonporous surface. The natural oils and residue on fingers leave a deposit on surfaces which mirror the ridges and furrows that are present on the individual’s finger.

The techniques used depend upon the type of material in this case A Plastic Bag is a Nonporous material. Hence

A powder technique is usually used to identify latent prints on nonporous surfaces such as glass, marble, metal, plastic, and finished wood. When powder is distributed on the surface, it adheres to the residue deposited from the finger’s touch, allowing investigators to find the print. Often times, to avoid smudging the print, a magnetic powder technique is used in which the powder is poured on the surface and then spread evenly over the surface using a magnetic force instead of spreading the powder with a brush. The color of the powder should contrast with the surface that is being searched to allow better visibility. For example, the investigator should use a white or grey powder if searching a black marble countertop for prints.

Attorneys should find out whether the crime scene technician who collected prints using fingerprint powder used a disposable brush. If a brush is reused in different locations at a crime scene or reused at another crime scene, the brush can transfer trace amounts of DNA evidence.

2)

Another popular technique for fingerprint location and identification used by both lab technicians and investigators at the crime scene is superglue fuming. Superglue fuming is a chemical process that exposes and fixes fingerprints on a nonporous surface. In the lab, the process works by using an airtight tank, known as a fuming chamber, to heat up superglue (liquid cyanoacrylate) which releases gases that adhere to the oily residue of print, thereby creating an image of the fingerprint.

Superglue fuming can also be performed at the crime scene. Rather than using a fuming chamber, crime scene investigators may use a handheld wand that heats up superglue and a florescent dye. Superglue fuming performed at the crime scene can be vital to preserve prints on items that are being sent to the lab via mail. One of the drawbacks is that if the evidence is fumed too long, it can distort the print, rendering it useless.