Bloodstains
Bloodstains play a crucial role in forensic science, particularly in criminal investigations. They can provide vital information regarding the circumstances of a crime, such as distinguishing between a suicide and a murder, and identifying potential suspects through DNA analysis. Historically, bloodstain evidence had limited utility, primarily focusing on blood typing to identify suspects; however, advancements in DNA technology have transformed bloodstains into essential tools for law enforcement. By collecting small samples from crime scenes, forensic scientists can analyze DNA and match it against suspects' profiles.
Additionally, the patterns of blood spatter can help reconstruct the events surrounding a crime, indicating the type of weapon used and the sequence of actions taken during the incident. For instance, the volume of blood loss from a wound can vary significantly depending on whether the victim is alive or deceased at the time of injury. In situations where bloodstains are not visible, forensic experts can utilize chemicals like Luminol, which illuminates blood traces even in small dilutions and does not compromise DNA integrity. Furthermore, tests can discern whether bloodstains are of human or animal origin, adding another layer of analysis to crime scene investigations. Overall, bloodstains are invaluable in piecing together the narrative of criminal events and aiding in the pursuit of justice.
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Bloodstains
SIGNIFICANCE: Bloodstains can be used by forensic scientists to determine if crimes have occurred in such situations as differentiating between a suicide and murder. They can also help identify perpetrators of crimes by allowing forensic scientists to reconstruct sequences of events and match DNA samples.
Before deoxyribonucleic acid (DNA) technology become widespread in law enforcement, bloodstain evidence was of only limited use to investigators, who used it mainly to match basic blood types. Blood-typing helped but generally served to narrow lists of possible suspects only slightly because of the small number of unique blood types carried by human beings. Now, with the prolific use of DNA technology, bloodstains are invaluable resources during crime scene investigations. By using swabs to collect small samples of blood left at crime scenes, detectives and forensic scientists can analyze their DNA and compare the results with the DNA of any suspects they take into custody.
In addition, spatter patterns of blood found at crime scenes help forensic scientists and detectives reconstruct what happens between victims and offenders. Blood drops and spatters often reveal what weapons were used, in what fashion, and in what order. For example, the amount of bleeding from puncture wounds made while victims’ hearts are still beating is much greater than the bleeding that occurs when the same wounds are made after victims are already dead.
When blood traces are not apparent to the naked eye, scientists use special chemicals to test for their presence. Such chemicals can reveal the presence of blood after perpetrators try to wash away all traces with strong detergents or even bleach. One such chemical, called Luminol, emits light when it comes in contact with blood and can detect bloodstains diluted up to ten thousand times. Luminol is especially useful in forensic work because it does not interfere with DNA testing or destroy potentially valuable evidence that may be needed later. Other analyses, such as precipitin tests, can determine whether bloodstains are of human or animal origin.
Bibliography
Dutton, Gregory. "Study Assesses the Accuracy and Reproducibility of Bloodstain Pattern Analysis." National Institute of Justice, 14 Dec. 2022, nij.ojp.gov/topics/articles/study-assesses-accuracy-and-reproducibility-bloodstain-pattern-analysis. Accessed 21 June 2024.
Genge, Ngaire E. The Forensic Casebook: The Science of Crime Scene Investigation. New York: Ballantine, 2002.
Lee, Henry C., and Frank Tirnady. Blood Evidence: How DNA Is Revolutionizing the Way We Solve Crimes. Cambridge, Mass.: Perseus, 2003.
Saferstein, Richard. Criminalistics: An Introduction to Forensic Science. 7th ed. Upper Saddle River, N.J.: Prentice-Hall, 2001.