Forensic Science Tools & Techniques
Forensic scientists have a unique job description that encompasses law enforcement, investigation and science; and must be trained in the use of a variety of tools and techniques to help them interpret the evidence that is found at the scene of a crime. These can include, among others: blood spatter analysis, DNA testing, blood typing, chemical analysis, footprint or fingerprint analysis, and ballistics.
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Definition of Forensic Science
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Forensic science is defined as the application of science in answering questions that are of legal interest. More specifically, forensic scientists employ techniques and tools to interpret crime scene evidence, and use that information in investigations. Forensic scientists and technicians come from a variety of academic backgrounds, although most have completed coursework in the life sciences, chemistry and law enforcement.
Types of Evidence
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Forensic scientists often work as generalists, meaning that they have expertise in working with a wide variety of evidence types. However, many also specialize in the use of certain techniques and tools. Different types of evidence require different skills and equipment. Types of evidence that are most frequently analyzed during investigations include: trace evidence and biological and ballistic evidence. Trace evidence is found wherever an object or person has had contact with another object or person and each of the objects leaves behind some sign of its having been there. Fingerprints and tire tracks are examples of trace evidence. Biological evidence will be found wherever there is bodily fluid or human or animal remains, and can include DNA testing. Ballistics is the study of firearms and, in particular, the path that a bullet takes during flight.
Biological Evidence
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In examining biological evidence, forensic scientists use tools both at the scene, and in the lab. When a forensic scientist arrives at a crime scene, he may look for human remains, blood or other bodily fluids and collect samples of any that are found. Because not all bodily fluids (particularly those that have been cleaned up after) are visible to the naked eye, the scientist can use the chemical Luminol to show latent traces of blood. Where large quantities of blood are present, an expert in blood spatter analysis can examine the patterns and size of the bloody areas to determine information such as the trajectory of the blood. This data can help an investigator deduce what type of weapon was used, or where the perpetrator and victim were standing during the attack.
DNA Evidence
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DNA evidence uses the unique genetic markers that identify individuals to determine whether a person was at a scene, or to identify a piece of property as belonging to a specific person. In order to identify an individual's DNA it must be extracted from a piece of property that a person has had contact with, and has left a bodily fluid such as semen, blood or saliva on. The scientist performs tests that identify genetic markers and create a profile that is unique to that person, and can be compared to a sample taken from any individual. Scientists may also attempt to get enough blood from evidence to conduct toxicology testing, to determine the presence of alcohol, drugs, poisons or chemicals.
Trace Evidence
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Trace evidence is found where two objects have made contact with each other. When a person or an object touches another object, some 'trace' of the two will be exchanged. This is the theory behind the analysis of fingerprints, tire and footprints, and fiber analysis. Technicians lift fingerprints from surfaces by dusting the area with a powder which sticks to the oils in the fingerprint. She then employs fingerprint lifting tape to take the print from the surface to the lab, where it can be analyzed. In the case of a footprint, tire track or other pattern that was left in an outdoor area, a forensic scientist can fill in the depression with plaster, which can be removed after it sets up. The casting is taken to a lab where it is stored until needed, or compared against a known sample, such as a suspect's shoe.
Ballistics
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Some forensic scientists specialize in the field of ballistics testing. Ballistics is a science that involves the science of the flight path that a bullet takes as it travels to its target. Trained ballistics specialists can glean a tremendous amount of information about the type of weapon that was used, the path of the bullet and more through the examination of the bullet itself. Guns produce a specific pattern of wear and grooves on bullets as they are fired, and this pattern is unique. By examining the bullets and test-firing weapons, an investigator can frequently either identify the type of firearm that was used, where it was fired from, or even match the bullet with a specific weapon.
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