Foot wear and gun evidence help Investigators apprehend suspects that otherwise may not have been prosecuted to the full capacity of the law. In order to prove a valid case in trial you must have proven techniques that exemplify criminal investigative technology. Photographs represent the truth depicting the crime scene as found “IN SITU”. The Judge and Jury alike deserve to see justice served with the utmost competency of the Investigator.
It is important to be able to tell if there are footprints left at the crime scene or not. Some of the factors of foot impressions are dust prints, mud prints and blood or other substance prints. Footprints can be placed on hard wood, carpet, tile, and linoleum flooring. Some of variants of the foot print include shoe size, shoe type, tread type, tread wear, stance of the suspect upright leaning right or left. Stride length is a legitimate way to figure out the height of a suspect.
Preserving shoe impressions on dusty areas may require the use of Electrostatic Lifting. The electrostatic process involves using a Mylar sheet of film and a roller. An electrostatic unit is placed over the Mylar sheet to lift the dust print onto the sheet.
Other processes for collecting footprint evidence include casting and using dye to produce a replicate of the footprint.
Walking Patterns
An Investigator is able to tell the direction that the suspect and victim were moving at the time of the criminal act by the direction of the footprints. The variable of the velocity the suspect or the victim was moving at during the criminal act can be surveyed by stride lengths and pressure put on the shoe print. Footprint evidence can also consist of the distance traveled before or after the criminal acts have occurred. The measurements taken of the footprints can identify whether the criminal act was premeditated, circumstantial or by impulse.
Gun Evidence
Gun evidence includes DNA, fingerprint, serial number, ballistics, shell, primer, powder, and pin. In general positive identification of the suspect is the prime target of evaluating a gun used in a criminal act. Linking the suspect with a gun is not an easy task. An Investigator must be 100% sure that the evidence they bring to trial is convincing enough to prove the guilt of a suspect without reasonable doubt.
Blood Evidence
Splatter of a gunshot wound identifies the direction showing the distance between the gun and the shooter. A close up gunshot wound will be larger than a gunshot further away. Depending on the calibre of the gun, the shot may curve, pass through the body, or enter other objects located in the vicinity. Placements of the gun such as straight, sideward, high, or low are depicted by the splatter pattern on close by objects.
Factors that determine the type of gun fired are the shell casings, rifling, bore, grooves and lands. When comparing bullets a comparison microscope is used to examine both the forensics ballistic round and the round found at the crime scene. Lands and grooves on the bullet after being fired are particular and unique to the gun fired. As the bullet travels down the bore located in the center of the barrel it is carried by a spiralling column called the riffling. The riffling adjusts the speed that the bullet travels. Determining the calibre of the weapon can be performed by examining the diameter of the bore.
One way to compare and analyze matching bullets is by analyzing the fire pin impression. The placing that the firing pin strikes the bullet pin allows the test examiner to identify whether a bullet was fired from the same gun or not.
Gunshot residue (GSR) is left on the crime scene it can be located on the suspects hands and clothes. Traces of GSR can be examined by performing tests for nitrate, chemical tests include the Walker test and the Griess test these tests for lead and barium help Investigators find the nitrate located on the suspect.
When analyzing the cartridge of a weapon the ballistics information can be found in the Integrated Ballistic Identification System (IBIS). This ballistics database founded by the Bureau of Alcohol, Tobacco, Fire Arms and Explosives identifies bullets and cartridges by incorporating two programs the first Bullet Proof a bullet analyzing module and the second Brasscatcher a cartridge analyzing module. Later in 1999 the FBI and ATF released the National Integrated Ballistics Information Network (NIBIN). This new national ballistics network incorporates DRUGFIRE and IBIS to identify bullets and casing across the United States. (Saferstein, 2006) When analyzing footprint and gun evidence an Investigator must be thorough to use the best known technological techniques in order to present a competent trial examining all aspects of the crime scene making sure that the suspect is 100% guilty of the crime.
References
Saferstein Richard (2006) Pearson Prentice Hall Criminalistics an Introduction to Forensic Science
