Alone, hydrogen peroxide is also useful because it produces white foam from the formation of oxygen bubbles by the catalase enzyme in blood, which can easily be observed. 3 Thus, it would be best applied when there is ample blood evidence to perform other confirmatory and DNA tests. 3 While the Kastle-Meyer test is affordable and quick, it cannot be applied directly to the bloodstain because it destroys DNA evidence. 3 When the solution changes from colorless to pink with the addition of hydrogen peroxide, blood is present.
In the Kastle-Meyer test, a blood sample is treated with ethanol and phenolphthalein, a colored indicator. Fortunately, there are many tests to aid analysts. Often, blood is hard to detect, especially if criminals attempt to conceal the evidence by washing it away or using cleaning products. 1 However, when chemical tests are necessary, they are utilized based on whether the suspected blood is visible or not.
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Typically, analysts will first use the Appearance, Behavior, and Context (ABC) Approach to Bloodstain Verification because it can be impractical to test an entire crime scene for blood. To classify blood and perform a thorough analysis, its presence must first be detected and confirmed. To combat this problem, new, computerized methods are being tested to improve scientific accuracy and the reliability of the legal system. The discernibility of bloodstain evidence can be difficult for analysts and is further complicated by other environmental and health factors that contribute to bloodstain appearance. 1 While BPA is heavily relied on in the forensic science community, its validity is becoming questioned. 1-2 His description of velocity impact spatter being low, medium, and high is still employed in the field today. Paul Kirk made contributions to blood spatter analysis by categorizing blood by size and speed at which it hits the surface. After the presence of blood is confirmed, it is then classified. Thus, it is imperative to have methods of blood detection that simultaneously preserve the genetic information. Additionally, because blood is rich in DNA, it can also be used to generate a DNA profile to match either the suspect or victim. Blood evidence is crucial in criminal investigations because it can corroborate or dismiss a witness’s account of the crime. KEYWORDS: Bloodstain pattern analysis, luminol, DNA, impact spatter, directional analysisīloodstain pattern analysis (BPA) is one of the subcategories in the field of forensic science. Future research into analytical methods could allow blood pattern analysis to become a more reliable area of forensic science. Current classification methods will be discussed as well as new, emerging methods. This review will focus on how blood is detected and classified and include certain factors that may affect blood appearance. However, analyst error sometimes results in inaccurate conclusions. The shape and convergence of bloodstains can infer the murder weapon and origin of attack, which is crucial when reviewing witness statements.
Bloodstain pattern analysis is a subfield in forensic science that utilizes blood evidence to reach a conclusion about a crime. When a violent crime occurs, blood evidence is found at the crime scene.
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