Integrating Forensic Science: Physics-Based

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Introduction
For the past two decades or so, television shows, books, and movies that portray detective work and forensic science have become increasingly popular among readers and enthusiasts. They demonstrate that science is an important tool in answering difficult questions regarding how the tragic assassination of President Kennedy happened for example. Forensic Science is appealing to many people because they want to be detectives to solve problems and puzzles. Today I will focus on how scientific principles embody the study of forensic science but with a main focus on how physicists and crime scene investigators use physics, among other sciences, to solve crime cases in forensics.

Forensic Science is a multidisciplinary that embodies concepts in many areas including but not limited to biology, chemistry, anatomy, genetics, physics, and math. Forensic Science appeals to the natural detective in some people and also to those who like to solve complex puzzles. The ultimate goal is to make sense out of complex problems that require reasoning and involve numerical data, evidence, and uncertainty.

Many areas are studied in Forensic Science for example fibers are primarily chemistry-based while other sciences are required for characterization of evidence as well as assessment of its forensic value. Other principles are shared among math, biology, and physics. Statistics, in this case, is used to access the probability of a fiber linked between suspect and victim (math) as well as microscopic observation used to differentiate natural and synthetic fibers (chemistry). Also since fibers are pieces of evidence that can be found at a crime scene; the presence of fibers may be considered trace evidence. Most trace evidence is not unique to an individual therefore comparisons must be made based on similarities and probabilities (1). Another important biological unit is on hair. This area of expertise requires a compound microscope to observe and characterize different types of human and animal hair. Physics and chemistry are also integrated into this area because physics is used to determine the diameter of a hair sample (1). To do so, investigators and/or scientists measure the distance between bright spots of interference patterns on hair, using a laser pointer. When this technique is used it demonstrates the wave nature of light; refractive index. Many of the properties of hair are related to the chemical composition and structure of polymeric proteins and can lead to further discussion and investigation of natural polymers including DNA. Serology incorporates both biology and physics. Biological principles are used to determine whether or not a particular stain is blood spatter patterns, measuring the angle of impact, finding the velocity at which the blood hit the object on which it spattered, measuring the distance from which the blood was dropped, and finding the direction from which it spattered. The application of trigonometry at this point is very important as well (1).

Infrared Spectromicroscope

Forensic Science is rarely absent from the news these days. Hardly a week seems to pass without reports of a criminal being convicted by DNA evidence extracted from a single hair; a flake of skin or a trace of blood or saliva found at a crime scene. Many, of the materials encountered at crime scenes are too small to be analyzed using standard instrumentation, even at infrared wavelengths. However, the advent of “infrared spectromicroscopy” has led to significant advances in forensics.

Infrared spectroscopy is extremely powerful because infrared photons can couple directly to certain vibrational modes of molecules. Ultraviolet light excites broad electronic transitions, meaning that it cannot uniquely identify samples by measuring the frequency of vibrational modes of the compounds in a sample (2). Infrared spectroscopy has already been used to study a diverse range of samples, including crops, soil, thin films,...
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