Unit IV: Forensic Tools and Techniques 1 After evidence is collected from a crime scene, that information is transferred to a medical facility for forensic testing

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Unit IV: Forensic Tools and Techniques 1 After evidence is collected from a crime scene, that information is transferred to a medical facility for forensic testing. Testing may include examining small objects under a microscope, checking for firearm residue, observing matter through light and in glass, collecting hairs and fibers, and reviewing drug and toxicology levels.

The purpose of these investigations is to scientifically prove what exactly happened at the scene of the crime. In this section, we'll discuss the various tools used to examine different types of evidence. 2 The microscope: Trace evidence or samples of forensic science, at times, are microscopic. To analyze such different types of samples, scientists must use various types of microscopes.

Over the years, there have been many advancements in using the microscope in forensic investigation. The microscope is a tool that is used to examine matter and is an important tool used in many branches of science to examine small objects and fine detail. The general uses of a forensic microscope are to locate, identify, and recover any potential evidence in order to be used in comparison with other like evidence.

Examples of trace evidence include hair, fiber, paint, body fluids, chemicals, or any other particles left behind during a crime. Generally, the microscope is one of the most important and significant tools used to identify trace evidence as well. It is also important in the reconstruction of past events.

With the microscope, scientists are able to analyze small objects and matter to distinctly identify its relation to the scene of the crime. The primary goal is to observe, record, and gather evidence in order to establish a legal case or to solve a crime. As modern science and computer technology advances, automated microscopy enables scientists, medical professionals, and law enforcement personnel to solve criminal cases faster and more efficiently. 3 Firearms, tool marks and other impressions: Most people do not realize that their DNA or an element of their body may transfer onto any object or any surface. When firearms are used in the commission of a crime, evidence such as fingerprints, chemical residue, and marks are found at the scene of the crime.

For example, when an individual fires a weapon, the residue from both the primer and the propellant — the chemicals — are forced forward out of the barrel and also escape through the chamber backwards towards the individual firing the weapon. 4 Firearms and tool mark examiners provide reliable scientific support at both the investigation and during stages of the criminal court proceedings.

Information may include the type of weapon used, particular type of bullet that was fired from the weapon, whether the bullet was fired from the suspect’s weapon, whether a tool found in a suspect's possession was used at the scene of a crime, original serial number of a weapon or other metal object, if gunpowder is present on a victim’s clothing or on a suspect, and the distance from the muzzle of the firearm to the target at the time the weapon was fired.

Residues and DNA are collected at the scene of a crime by swabbing, vacuuming, and taping different pieces of evidence. The most convenient method for collecting residues is by taping the evidence with adhesive tape. The information collected is then tested to understand both the disposition and the subsequent analysis of the residues. This helps to determine who fired the weapon or who was close to the weapon when it was fired as well as the victim’s distance from the weapon. This could also corroborate information from suspects — victims and witnesses. This information will then be used to provide the facts of the case during the criminal trial. 5 Matter, light, and glass examination: Small particles such as matter, light, and glass provide insights to the events that transpired at the scene of a crime.

Matter is anything that has a mass and occupies space. All of these elements are listed by name on the periodic table. The forensic scientist must determine distinguishing characteristics of a particular source of matter that could be uniquely identified. Physical properties of matter may include weight, volume, and color.

This information is crucial as a source of evidence, thereby linking a suspect to the criminal act and even the crime scene. This information is collected at the crime scene and analyzed at a forensic laboratory to determine the facts of the case. 6 At times, glass may be broken during the commission of a crime.

In most situations, glass evidence is in small fragments that are recovered from the ground, soil, clothing, etc., and then compared to what is known as the controlled sample. The original item, such as the window glass at the crime scene, may be found in the victim or suspect’s hair, on his or her clothing, or on his or her shoes.

For example, in a vehicle hit -and -run accident, there are many clues that could be assessed at the scene of the crime. There may be fragments of broken glass from the vehicle that may be found on the victim. Small pieces of evidence may help to identify the victim that was involved in a crime.

No matter how small the evidence is, it helps paint a larger picture to the series of events. 7 Hairs and fibers: Hairs and fibers contain evidence such as DNA that directly links a person to the scene of a crime. This source of information provides clues as to what took place.

Overall, hairs and fibers are the most common trace evidence found and processed in the forensic lab. What is most common for violent crimes is the transfer of this evidence from the criminal or suspect to the victim or crime scene and vice versa.

Hairs and fibers are extremely important in identifying key evidence in a crime.

Hairs and fibers can be easily transferred from person to person, people to objects, objects to people, and from objects and people to the environment. Essentially, it has been discovered that hairs and fibers do not degrade over time as fast as one thinks.

This leads to the ability to collect evidence well after the commission of a crime. Hair, at times, is individualized by DNA analysis.

Although not conclusive, hair and fibers may be used in establishing whether a suspect is guilty or innocent. 8 Drugs and forensic toxicology: Drugs and toxicology test the contents within a person's body. Information garnered from this study may explain the individual's mental and physical state. Forensic toxicologists perform scientific tests on bodily fluids and tissue samples to identify any drugs or chemicals present in the body.

Scientific results are used to explain the person's behavior before, or during, or after the commission of a crime. The forensic scientist’s main goal is to determine the following: whether or not a controlled substance is present, to determine how much of the substance is present, and determine the relationship of drug samples to one another.

The forensic toxicologist’s role is to detect and identify the presence of drugs and poisons in bodily fluids, tissues, and organs. Generally, the widespread use of drugs and substances means most are of a toxic nature. This means that forensic analysts must have a means of extracting the drugs from their metabolites and then identifying them.

For example, a drug -facilitated sexual assault is sometimes known as date rape. In this crime, the perpetrator administers drugs, usually through alcoholic drinks to the victim prior to a sexual assault. Understanding the effects of drug and alcohol on an individual helps to evaluate the scene of a crime. 9 Summary: After evidence is collected from a crime scene investigation, it is transferred over to a medical facility laboratory for forensic testing. Testing may include microscopic examination and the collection and examination of firearm evidence, hair, glass and fibers, as well as reviewing toxicology reports. Most people do not realize that their DNA or an element of their body may transfer onto a subject or object.

Most importantly, this information can be used to link a suspect with the scene of a crime. 10 11