Saliva as evidence
Saliva, a complex fluid secreted by the salivary glands, serves various functions in the human body, including aiding digestion and maintaining oral hygiene. It contains a mixture of water, electrolytes, enzymes, and protective substances, making it beneficial for digesting food and preventing bacterial growth. In forensic science, saliva is recognized as an essential tool due to its ease of collection and the valuable information it can provide, including blood type and DNA for identification purposes. Saliva can also indicate drug use and certain health conditions, as it may contain markers for various diseases. The methods for testing saliva can be classified into destructive and non-destructive approaches, with non-destructive methods retaining the sample's integrity for further analysis. Overall, saliva plays a significant role not only in health and nutrition but also in forensic investigations, linking individuals to crime scenes through biological evidence.
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Subject Terms
Saliva as evidence
DEFINITION: Complex fluid mixture secreted from the salivary glands into the mouth or oral cavity.
SIGNIFICANCE: Saliva is an extremely useful tool in many forensic applications, in part because collection of saliva samples is relatively simple and noninvasive. Even small samples of saliva will yield the donor's blood type as well as DNA for comparative purposes.
Saliva contains water, electrolytes, mucus (consisting of mucopolysaccharides and glycoproteins), various enzymes, and opiorphin, a pain-killing substance. Saliva has many functions in the human body. It aids digestion by moistening food, binding it together so that it may be more effectively chewed. It also lubricates food, permitting swallowing and easy passage of food down the esophagus, thereby minimizing irritation of the lining of the oral cavity. The salivary enzyme amylase initiates digestion of carbohydrates such as starch, and the addition of saliva enables food and liquid molecules to more readily interact with the taste buds on the tongue, thus enhancing taste.
Saliva aids oral hygiene by flushing food debris from the mouth. It contains the enzyme lysozyme, which destroys many bacteria, thereby acting as a disinfectant; however, many pathogenic bacteria can thrive in the mouths of humans and other animals. Saliva also functions as a protective barrier, as when nausea reflexively triggers saliva flow, which coats the oral lining and teeth before vomiting occurs so that acidity is minimized.
The amount and type of saliva secretion is controlled by the autonomic nervous system. Increased stimulation leads to increased blood flow to the salivary glands, which stimulates production and release of saliva. Sympathetic stimulation results in an increased amount of mucus in the saliva, and parasympathetic stimulation results in increased volume of watery saliva production (serous saliva).
Saliva samples are often important in criminal investigations. Collection of saliva is relatively simple and noninvasive, and only a small amount is needed for determination of an individual’s blood type and for extraction of DNA (deoxyribonucleic acid) for comparisons. Saliva can also reveal the drugs an individual has taken; in some cases, even simple contact with certain drugs can be detected through analysis of saliva.
Saliva samples also permit evaluation of general health, and saliva tests have been developed for the detection of certain medical ailments, such as human immunodeficiency virus (HIV), and other health problems. Saliva samples that reveal the presence of viral, bacterial, or systematic diseases may link their donors to crime scenes or to objects. Furthermore, the presence of certain bacteria not identified with other bodily fluids can help investigators in determining that fluid samples are saliva.
Saliva may be tested using various methods. Generally, these tests are classified as destructive or non-destructive. Non-destructive methods preserve the integrity of evidence, which can then be used for further processing such as DNA profiling or saved.
Bibliography
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