Pattern Evidence for Forensic Chemistry Class

Pattern Evidence for Forensic Chemistry Class

Pattern evidence is defined as any forensic evidence that can be read and analyzed from a specific type of pattern left by the physical contact between different people (such as victim and assailant), persons and objects (such as victim and automobile), and different objects (such as automobile and tree). These types of pattern evidence can result in various designs such as depositions, imprints, recesses, residues, and striped markings.

Over the past decade, traditional forensic investigative techniques have increasingly been employed for environmental protection. Recently, physical science professionals have suggested that use of chemical fingerprinting and geochemical tracking to attribute liability at chemical contamination sites is helping to define the emerging discipline of environmental forensics. Several legal instruments prevent and restrict the taking of wildlife and plants from the environment(Carpi & Mital, 2000). Hunting regulations establish limits on the types or numbers of animals that can be killed, seasons in which hunting is allowed, and methods of legally permissible hunting. Land regulations, such as laws defining wilderness areas or private property, establish boundaries on the locations from which animals and plants can be collected. Violations of the legal premises of these laws result in crimes against the environment for which forensic techniques are becoming increasingly applicable in criminal investigations. Although DNA fingerprinting has played a major role in many endangered species cases, the method has limitations. Degradation or intentional alteration of sample tissue can hamper DNA analysis. The method also requires the compilation of large databases that represent sufficient intra- and interspecies genetic variation to accurately identify members of the protected species.

According to the Centers for Disease Control, firearm related injuries were responsible for over 68% of homicides and were one of the three leading causes of injury related deaths in the United States in 2008.1 Effective ballistic investigations act as a deterrent and reduce the number of firearm-related crimes in the United States (Bueno et. al. 2012). The development and innovation of new methods will meet the demand for ballistic investigations which draw more definite conclusions. Therefore, an increasing number of modern analytical techniques have been applied to this field of forensic ballistics and trace evidence analysis in recent years. These investigations are designed to match a suspect to a crime but require the recovery of physical evidence in order to make the most confident conclusions

According to the theory of GSR particle origin, most GSR leave the firearm after the discharge in the form of a gas (Abrego et. al. 2012). This gas gradually condenses, and individual particles sediment around the discharged firearm, including on the shooter's hand.3 The majority of GSR particles are typically in the range of 0.5 to 5.0 µm in diameter. Gunshot residue (GSR) consists of solid particles produced when a firearm is discharged, and its detection provides very important evidence in forensic investigations(Weber et. al. 2011)

Specific examples of sources that often result in pattern evidence include blood splatters (such as from a bullet's exit wound), ...