The Examination of Forensic Firearms: the Crime Scene Through Microscopic Imperfections - Research Paper Example

Running head: Footwear and Firearms Evidence Recently, science has brought considerable assistance to the detection of crime. Since in the physical universe everything is potential to become an evidence item in an investigation, a range of procedures may be useful in the analysis and interpretation of evidence in a criminal case. During criminal investigation, determining and proving whether a particular individual(s) was or was not present at the crime scene is vital. Hence, in the community of law enforcement, physical evidence collection, preservation and analysis is of great importance. This paper discusses the value of footprint or footwear evidence, preservation and photographing of the evidence and casting of the impressions. It also discusses the procedures used in the examination of firearms evidence. Introduction Footwear is an example of primary evidence. It is very important because on its own, it is potentially conclusive without other strong evidence. There are at least three forms of footwear evidence including footwear insole impressions, footwear trace evidence and footwear outsole impressions. Whenever something comes into physical contact with another, it either leaves a portion of itself or takes a portion of the other. This is a theory that Edmond Locard developed and that crime scene investigators and physical evidence analysts use. They hold the assumption that since criminals must enter and exit the scene of crime, there may be traces of their footwear. To avoid eyewitness identification and leaving fingerprints, criminals frequently wear masks over their faces and gloves over their hands respectively. However, they make little effort to cover up footwear. Footwear evidence therefore, when the investigator of a crime scene properly collects and preserves it and a footwear expert examines it in detail, becomes an important source of evidence during criminal investigation that proves or disproves an individual’s presence at the scene of crime. Unfortunately, disorganization or failure to secure the scene of a crime properly may result in the destruction or overlooking of this form of impression evidence. Investigators use footwear evidence to obtain valuable information that can enable them to locate a suspect. For example, it can lead to positive recognition of the particular known shoe that made the print (Hilderbrand, 2009). Footwear evidence is very useful in cases where proof of the presence of an individual is incriminating such as rapes, robberies, homicides, burglaries, assaults among others. Footwear evidence is of great value as it can provide the make or the unique characteristics of a shoe, its type or brand by comparing it with a database as well as its estimated size. It can also help in proving or disproving an alibi, crime scene reconstruction, the identification and elimination of a suspect, determining the number of perpetrators, their gait characteristics and their path into and away from the scene of crime. Other uses include determining the events that took place during the crime and their sequence, the period when they made the impression among others (Academic.evergreen.edu, n.d). The first responding officer at the scene of crime is responsible for the protection of the scene and the preservation of evidence for further investigation. On arriving at the crime scene, one of his or her first considerations should be footwear evidence. He or she should evaluate and attempt the determination of the whole area of the scene of crime, including entry and exit paths and other areas that may prove that a perpetrator was present. He or she should then secure the area completely and mark evidence for subsequent documentation and collection. It is also necessary for the officer to isolate the crime scene area to prevent crime scene-unrelated newly made footwear impressions. In addition, agents such as automobiles, weather and people approaching the crime scene from the same paths of entry and exit that the suspect might have used can easily obliterate footwear evidence (Fuller, 2008). The first responding officer marks off the crime scene large enough using crime-scene barricade tape until the arrival of the crime scene investigator. Where weather might affect the footwear evidence, he or she may place cones or boxes over the impressions until the crime scene investigator arrives. On arriving at the crime scene, the crime scene investigator should conduct a search on the secured area thoroughly and systematically. He should carefully photograph and document with regard to the exact position of each footwear impression and its surroundings – a procedure that should precede the performance of any other search. On locating footwear impressions and marking them as to their location, the crime scene investigator should then complete the processes of photographing, casting and collecting. Prints and impressions are the two forms in which footwear evidence occurs in almost all crime scenes. Although the recording techniques in such evidence may vary, the search is essentially similar. The investigator should always use a systematic searching method – he or she should never blind search the scene of crime. While photographing, the investigator should give priority to footwear evidence located outdoors to ensure that it is not destroyed while he or she is inside. To locate footwear impressions, the crime scene investigator, at an oblique angle, casts a strong white light with a directional beam (a forensic light source) over the surface. On locating the impressions, the process of collection and recovery starts. The investigator should photograph, document, lift and/or cast all impressions (Hilderbrand, 2009). Casting recovers larger impressions that are three-dimensional including footprints that perpetrators may have left in mud, blood, dust, oils among others. During the casting process, the investigator pours a substance into the impression, hardens it and then removes it thereby yielding a cast of the impression on the ground. Although investigators use a variety of products in the creation of casts, the best casting material is dental stone owing to its accuracy, ease of use and strength. The difference between a cast and a photograph or lift is that a cast is a three-dimensional structure that provides a positive footwear reproduction while the rest provide two-dimensional print reproduction. These can be recorded variously using electrostatic lifting apparatus, photography and gel-lifts and enhanced by means of dyestuffs. Lifting applications include placing a contact/adhesive paper over the footwear print in very light dirt or dust. The impressions are transferred to the adhesive side of the paper; the impression is peeled off from the paper and then photographed (Fuller, 2008). Firearms evidence examination procedures Usually, firearms evidence is encountered in crimes against persons including homicide, robbery and assault. Other crimes in which it is encountered include rape, narcotics violations and burglary. The most common and requested examinations are cartridge cases’ and bullets’ comparisons to specific firearms. Other possible examinations include firearms examination for modification or functioning, ownership tracing, determination of distance based on shot spread or powder residue, list of possible weapons perpetrators may have used, fired shots trajectories and sequence and restoration of serial number. The firearms analysis examiner can detect the evidence of handling a firearm or firing by analyzing the residue of gunshot collected from a person’s hands or other body surfaces. He or she should examine the firearm for likely trace evidence such as hair, blood, paint, tissue or fibers, which may be relevant. If in doubt, he or she should not dust the firearm for prints. He or she should submit the firearm to the laboratory personally and request for the processing of the firearm for prints. Some cases, like alleged gun struggles and suicides require the determination of the distance between the victim and the gun muzzle. The investigator should examine garments for powder residue and other close firing indications (Layton, 2008). The examination of forensic firearms is based on the identification of firearms, which involves the identification of a cartridge case, bullet, or other component of ammunition as having been fired in or by a specific firearm. The firearms analysis examiner identifies firearms utilized in the crime scene through microscopic imperfections produced in gun barrels unintentionally during their manufacture. He carries out bullet comparisons by test-firing bullets from a firearm and comparing them to those found in bodies or surfaces at the crime scene. In this analysis, he identifies the class characteristics of the firearm, which include its shape and size, metallic composition, type and caliber, markings of the firearm’s manufacturer and its weight. He also identifies individual bullet characteristics such as striation marks resulting from the bullets passage over the groups and lands of the individual weapon as it passes through the barrel. He uses a comparison microscope to match patterns. This helps the examiner to determine whether a particular firearm fired a particular bullet. He may also determine a projectile’s point of entrance and exit in metal, wood, glass or clothing. The examiner also carries out cartridge case comparisons. He determines whether markings on an evidence casing resulting from firing in a firearm are similar to those on cartridge casings resulting from test firing the firearm. He uses the comparison microscope to compare the markings on the test cartridges and on the evidence (Lee & Harris, 2000). In addition to the examiner’s preliminary examinations and research and the microscopic analysis, he can conduct a variety of tests and procedures. These include trigger pull tests for the determination of the amount of force required in firearm discharge, accidental discharge tests for the determination of whether a firearm can fire without directly applying pressure on the trigger and silencer testing for the determination of possibilities of classifying certain muzzle attachment as sound suppressors. There are also function tests for the determination of whether a firearm is operating normally and fully in all its fire modes and whether there is proper operation of all safeties and full auto conversion tests for the determination of whether there is modification of a semi-automatic firearm to fire automatically. Others include trajectory analysis examinations for the determination of the direction and angle of fire and the shooter’s positioning or location through the geometric analysis and measurement of bullet holes and shot pattern examinations for the determination of the shooter’s distance from a target among others (Schehl, 2000). Conclusion It is important to note that the role of any examiner or investigator does not end until he or she testifies in court about his or her evidence. He or she should therefore ensure that he/she maintains great accuracy and care. In so doing, he or she does not have to fear the attack of the defense attorney. He/she does not need to speak much in defense of his or her evidence or report. Instead, they will bear mute witness against the perpetrator. This is because properly collected, documented, preserved, analyzed, interpreted and examined evidence is factual- it can never be wrong or bear false witness, it does not forget, it is never absent or confused. Only human failure to or in finding this evidence, studying and understanding it can diminish its value. References Academic.evergreen.edu, (n.d): Fourier Transform Infrared Spectroscopy and Forensic Footwear and Tire Track Evidence. Retrieved November 29, 2009 from http://academic.evergreen.edu/curricular/fcb/ftirimpressions.doc. Fuller, J. (2008): How Impression Evidence Works. Retrieved, November 28, 2009 from http://science.howstuffworks.com/impression-evidence.htm/printable Hilderbrand, D.S. (2009): Footwear, the Missed Evidence. Retrieved November 29, 2009 from http://www.crime-scene-investigator.net/footwear.html Layton, J. (2008): How Crime Scene Investigation Works. Retrieved, November 29, 2009 from http://science.howstuffworks.com/csi4.htm Lee, H.C., Harris, H.A, (2000): Physical evidence in forensic science. Retrieved, November 29, 2009, from http://books.google.co.ke/books?id=2UKL_nIsJEwC&pg=PT183&lpg=PT183&dq=examination+of+firearms+evidence&source=bl&ots=pWw7ZbqeVK&sig=P1lyfL2WuASgA7kcFs3TDrIJigk&hl=en&ei=_9QXS4SjH5Ky4Qai7pztAg&sa=X&oi=book_result&ct=result&resnum=6&ved=0CBoQ6AEwBQ#v=onepage&q=examination%20of%20firearms%20evidence&f=true Schehl, S.A. (2000): Firearms and Toolmarks in the FBI Laboratory. Retrieved December, 1, 2009, from http://www.fbi.gov/hq/lab/fsc/backissu/april2000/schehl3.htm#Index3 Read More