Latent fingerprints refer to marks found at crime scene which may be invisible to naked eye. If fingerprints at crime scene are noticeable, for instance left on some other discernable medium such as blood), they are not latent fingerprints. Usually, forensic experts use fumes, fingerprint power and other procedures to unmask latent fingerprints found at crime scene. Majority of forensic experts have specialized in recovering fingerprints that can be used to apprehend criminals. There are many sources of latent fingerprints. These includes: blood; sweat; paint; and bodily fluids. During forensic analysis of the latent prints, the expert tries to ascertain the source of the print in order to determine the identity of the criminal (Smith, 2011, p2).
The processes I will use for latent impressions at the scene
As a forensic investigator, I will process the following fixed items for latent impressions: the counter; the ice cream cooler; and the beer cooler. One of the first things I will do after the crime scene has been photographed is to dust these items for latent fingerprints. By doing this, I will ensure that all marks of fingerprints are revealed. I use a specialized finger print powder to brush over the counter, the ice cream cooler, and the beer cooler to see if any fingerprints will surface. In case some prints appear after dusting, I will photograph and then lift them carefully using a transparent tape before appending to fingerprint cards. In case I encounter difficulties in retrieving prints from the beer and ice cream coolers, I will use another procedure called fuming to locate latent fingerprints. Fuming induces a chemical reaction with trace materials left behind by a fingerprint (Smith, 2011, p3). Therefore, the main reason for dusting and processing latent prints is to make them noticeable so that they can be used to identify the criminal.
Items that will not be processed for latent impressions
As noted above, the latent impression is a process that is only used when fingerprints are not visible to the naked eye. For that matter, I will not use the procedure on the Lottery Ticket and the blue steel.38 caliber revolver because they both have visible fingerprints and therefore do not require enhancement. I will simply photograph them without additional processing (Fingerprint Identification, 2011, p.1). After collecting al the fingerprints at crime scene, I will take them to a crime lab for further analysis.
The processing protocols for each item
When the prints are submitted to the lab, they are scanned and cross-checked using a computer to compare them with criminal database for matches. For example, the Integrated Automatic Fingerprint Identification System (IAFIS) is used by the law enforcement agencies in the United States to acquire additional information on fingerprints retrieved at crime scenes. IAFIS has over 46 million records and is used to compare prints from the crime scenes. The IAFIS record has information from citizens as well as criminals whose fingerprints are collected on regular basis (Smith, 2011, p4).
The blood samples and hair-like fibers found on the gun can be analyzed using a DNA testing procedure to give important information about the criminal. After the blood sample and the hair-like fibers are received at the lab, their DNA must be extracted. Then the DNA is split into smaller pieces using a specific restriction enzyme. The digested fragments of DNA are then placed into a square-shaped gel. The DNA fragments form bands and moves to one end, with the smaller fragments moving faster through the square-shaped gel. The DNA is then moved to a membrane; which is later dipped in a liquid with radioactive DNA probes. The DNA probes attach to their structural complement. Meanwhile, the radioactive indicator of the probe stimulates the probe bound piece to light up. As a result, the position of the probe bound piece is known. After surplus probe is cleared, the membrane is aligned to X-ray film where black bands surface. This image is referred to as autoradiograph. The X-ray pattern is determined by the period the membrane is exposed to the film. Finally, a comparison is made between the criminal’s autoradiograph and the one generated by the blood and hair samples acquired from the gun (Sigh & Aggarwal, 2011, p.1).
The procedure used to analyze prints found on the cigarette is similar to the methods employed for fingerprint analysis. The forensic experts at the lab compare prints found on the cigarette with known samples from the database. First, the fingerprint experts compare the patterns of the ridge and then searches for ridge characteristics. According to the U.S. regulations, there must be at least 12 points of similarities for any print identification to be authentic. The FBI has a print classification system that uses Henry Fraction to allot numerical values to general patterns on a whole set of ten fingerprints. This permits millions of fingerprints to be coded and filled in an efficient manner. After evidence of fingerprints is photographed, they are delivered to the lab for analysis. Next, the fingerprints (such as those found on the cigarette butt, spilled cigar box, cardboard carton, the map and the six pack container of cold beer) are dusted. This is because human fingers are naturally oily. When someone uses his fingers to touch a smooth surface, oil is released from the ridges. Thus, when the surface is powdered, the powder attaches itself to the oil and reveals the fingerprint pattern. Fluorescent powder is best used reveal to prints found on the cigarette butt, spilled cigar box and the cardboard carton (Banning, 2010, p.7).
All fingerprint evidences eventually are submitted to a crime lab where they are compared with existing data for identification purposes. For example, the spent bullet wall is not retrieved from the wall; rather, the entire area where the bullet is clogged is cut out. The gunshot residue must be submitted and analyzed in the lab within six hours to match it with target residue. Each person has a unique handwriting. For this reason, document examiners can use the crude map and the piece of note paper found at the crime scene to make comparisons in handwriting. Computer forensic experts can later retrieve slack data and logs and use it to identify the criminal (Banning, 2010, p.8).
As a crime scene investigator, I will begin by introducing myself to all people present at the crime scene. Next, I will ask if there are any people who witnessed the homicide. Next, I will take their personal details promise to contact them if need be. I will also look out for individuals who seem nervous or have blood stains on their cloths.
How I would package the evidence pertaining to the fingerprint analysis
With regard to the blood stain found on the gun, I will place the weapon in a box, seal and label it then dispatch the evidence to crime lab for further analysis. Moreover, I will ensure that the gun is not loaded before I pack it. I will record the serial number, the model and the type of the gun before sending it to the lab. I will also wrap the bullet recovered at the scene in a paper and seal it in another labeled envelope. I will also recover all the hair-like fibers at the scene. I will use my fingers or tweezers to pick the hair strands from the floor, put them in a coin envelop which I will later fold and seal it in a bigger envelop. I will then label the envelope. I will use the same procedure for the cigarette butt, spilled cigar box, the crude map and the six pack container of cold beer (Andrus, 2000, p.8).
Andrus, R. (2011). Evidence Collection Guidelines. Web.
Banning, M.C. (2010). Impressions, Fingerprints and Trace Evidence. Web.
Fingerprint Identification. (2011). How Ridge Detail can assist in Crime Scene Investigation. Web.
Sigh, A., & Aggarwal, T. (2011). The Double Helix Unraveled: Evidentiary Aspects of DNA Fingerprinting. Web.
Smith, S.E. (2011). What are Latent Fingerprints? Web.