Crime scene technicians are responsible for photographing, looking for latent prints, and collecting evidence at crime scenes. Because of crime volume, crime scene technicians do not respond to all crime scenes. Many departments rely on specially trained officers or public safety aides to handle crime scene processing of less violent offenses, such as motor vehicle thefts and burglaries of homes and vehicles. Training of officers for this time-consuming and methodical work is often a limited, one-time event. Refresher courses on crime scene processing are typically not offered, providing minimal assurances that officers are following protocol or handling evidence properly. Without periodic training, officers are also not exposed to changing technology or more efficient methods of crime scene processing and evidence collection. Challenges of Crime Scene Processing
Every crime scene is different and involves decisions such as whether to process evidence at the scene, collect evidence for later processing at the crime laboratory, or request assistance from the crime scene unit. When deciding how to approach latent print processing, factors that may affect the method include weather conditions, contamination of evidence, and whether the evidence is on a porous or nonporous surface. Weather becomes an issue when it is raining and the officer is faced with processing a soaking-wet vehicle. The best course of action is usually to tow the vehicle to a police facility to allow the vehicle to dry before processing. If this is not an option, the second-best option is to ask the victim to call for processing when the vehicle is dry. If neither of these options is available, the officer is often limited to processing items inside the vehicle for latent prints and possible DNA. Touch, wear, or saliva DNA can often be found in a burglarized vehicle. DNA should be the officer’s first focus. Collecting it would involve taking a sterile swab lightly dampened with distilled water and swabbing the steering wheel, turn signal, gear shift, and edges of the rearview mirror. Inside the vehicle, there may be other miscellaneous items that the officer may decide to swab such as drink cups or cans, cigarette packs, or cell phones. If the victim is available, the officer should ask him or her to carefully look inside the vehicle to see if they see anything that does not belong to them, and therefore may have been left by the perpetrator. After carefully collecting possible touch DNA swabs, the officer should process the following locations for latent prints:

• Dash and console
• Rearview mirror and all windows
• Metal portion of seatbelts
• Miscellaneous items in the console, on and under the seats, and on the floor
• Items contained in glovebox and trunk

The decision whether to process items found inside a burglarized home or vehicle often hinges on whether or not the item is porous or non-porous. Porous evidence consists of items that, when touched, will absorb fingerprint residue like a sponge. Examples would be unfinished wood, paper, cardboard, and fabrics. Non-porous evidence consists of items that, when touched, will preserve the latent print on the surface unless disturbed. Examples of these would be glass, metal, and plastics. Non-porous items can be processed at the crime scene using black or gray powder and a fiberglass brush. More advanced methods of chemical processing for non-porous evidence include superglue fuming and enhancement with powder or fluorescent dyes. If the officer suspects the object may have belonged to or been touched by the suspect, the best decision would be to collect and preserve the evidence for latent print processing in the crime laboratory. Porous items usually respond better to chemical processing methods, such as iodine or ninhydrin, than the application of fingerprint powder. Vehicles that have been exposed to rain or heavy humidity will often have damp miscellaneous paper items scattered in the vehicle or in the glove box that will need to be dried before processing. There are some chemicals, such as Oil Red, which develop prints on damp paper more efficiently than ninhydrin or iodine. Paper items that have recently been touched react well to processing with magnetic powder; however, as a basic rule officers should collect paper items and submit the evidence for processing in the crime laboratory. Specially trained patrol officers and public safety aides play a crucial role in solving crimes by assisting the crime scene technicians with less violent offenses. Periodic training in crime scene processing can assist these officers, which is beneficial to any police department. Citizens in the community who are victimized expect law enforcement to respond to burglaries and motor vehicle thefts and identify suspects. The more efficient officers are in processing evidence, the more time they will have to answer other calls.

SOURCE:
In Public Safety