User:GZhen/Edits Sandbox

Edits I made:

- Moved things around and added some more information for the introduction section.

- Added a sentence to support the Early History section

- Changed heading (Methodology) to Bloodstain types and created subheading on impact spatter

- Everything in the heading under Bloodstain types are my own words and information (with the exception of a few sentences).

- Added photo to the article to support Cast-off patterns

Bloodstain Pattern Analysis (BPA) is the study and analysis of the color, shape, and size of bloodstains to draw conclusions about the nature and proceedings at a known or suspected crime scene with the purpose of drawing conclusions about the nature, timing and details of the crime. The patterns of the blood stain can help in crime scene reconstruction. It is used to study homicide or other violent crimes that present of blood may be present. It is one of the several specialties of forensic science. The use of bloodstains as evidence is not new. Since the late 1950s, BPA experts have claimed to be able to use biology, physics (fluid dynamics), and mathematical calculations to reconstruct events at a crime scene, and these claims have been accepted by the criminal justice system.

Bloodstain pattern analysis has drawn considerable skeptical scrutiny since 2000. A comprehensive 2009 National Academy of Sciences report concluded that "the uncertainties associated with bloodstain pattern analysis are enormous" and that purported bloodstain pattern experts' opinions are "more subjective than scientific." The report highlighted several incidents of blood spatter analysts to overstate their qualifications as well as questioned the reliability of their methods.

Early history
Bloodstain pattern analysis has been used informally for centuries, but the first modern study of blood stains was in 1895. Dr. Eduard Piotrowski of the University of Kraków published a paper titled "On the formation, form, direction, and spreading of blood stains after blunt trauma to the head." He conducted his first experiments on rabbits. A number of publications describing various aspects of blood stains were published, but his publication did not lead to a systematic analysis. LeMoyne Snyder's widely used book Homicide Investigation (first published in 1941 and updated occasionally through at least the 1970s) also briefly mentioned details that later bloodstain experts would expand upon (e.g., that blood dries at a relatively predictable rate; that arterial blood is a brighter red color than other blood; that bloodstains tend to fall in certain patterns based on the motion of an attacker and victim). A 1952 episode of the police procedural radio series Dragnet made reference to bloodstain pattern analysis to reconstruct a shooting incident.

Acceptance as valid evidence in United States courts
Between 1880 and 1957, courts in Michigan, Mississippi, Ohio, and California rejected expert testimony for blood spatter analysis, generally holding that it added nothing to the jurors' own evaluations of bloodstains submitted as evidence. In 1957, the California Supreme Court became the first American court to accept expert testimony examining bloodstains, accepting as evidence the testimony of Paul L. Kirk, a professor of biochemistry and criminalistics. He would also testify in the Sam Sheppard case in 1966, when the wife of an osteopathic physician was beaten to death in her home, interpreting bloodspatter evidence as proof that the murderer was left-handed (Sheppard was right-handed). However, bloodstain pattern analysis would not begin to enter wide use until it was promoted by Herbert Leon MacDonell. MacDonell researched bloodstains with a grant from the United States Department of Justice, and which also published his research in the book "Flight Characteristics and Stain Patterns of Human Blood" (1971). MacDonell testified in court on multiple occasions as an expert of bloodstain analysis, and the legal precedent set by these cases led to its widespread use in American courts, although as early as 1980 some judges expressed strong doubts about its reliability, and it was not always accepted as evidence, especially in states with no prior rulings that relied on such evidence.

The first formal bloodstain training course was given by MacDonell in 1973 in Jackson, Mississippi. MacDonell taught workshops on how to conduct bloodstain analysis, and the newly trained bloodstain analysts, who often had received as little as 40 hours of instruction, in turn would give expert testimony in court cases. In 1983, the International Association of Bloodstain Pattern Analysts was founded by a group of blood stain analysts to help develop the emerging field of bloodstain pattern analysis.

Further investigation into its admissibility as evidence
Starting in 1995, court cases where bloodstain analysts disagreed with each other raised concerns of the discipline's prediction's admissibility as evidence in court. In 2009, the National Academy of Sciences published an examination of forensic methods used in United States courts which harshly criticized both bloodstain pattern analysis and the credentials of the majority of the analysts and experts in the field. Judges have largely ignored the report's findings and continued to accept bloodstain pattern analysis as expert evidence.

In 2013 Daniel Attinger, a fluid dynamics researcher at Columbia University, published a paper on bloodstain pattern analysis in Forensic Science International, finding that many of the central hypotheses of bloodstain analysis remain untested, and that existing analysts often made incorrect assumptions or other errors in their analyses. The paper also proposed fluid dynamics as a theoretical framework for solving these problems, and Attinger has continued to publish several papers exploring these concepts (as have other scientists as well). However, these papers are largely theoretical, and have had little impact on the use of bloodstain analysis in courts.

Bloodstain Types
The bloodstain can present itself differently depending on the situation, material, and angle it lands (eg. Bloodstain patterns it can be hard to examine on porous surfaces such as fabrics. Due to the nature of fabrics blood stains can become distorted. ) From the angle of impact that caused a blood stain, in order to determine the blood's origin and the amount of force behind it. The variations in external forces can cause satellite drops. A point of origin can be determined by finding the area of convergence of blood droplets. To find this point of origin, the shape of the blood and the length are often taken into account and the stringing method is implemented. This method involves drawing lines from each blood splatter and finding the area in which all the blood intersect. Additionally, the angle of impact as well as other external factors such as the material on which the blood falls can change the shape and size of the blood. The point of impact can change the shape of the blood stain. Bloodstains instead of maintaining it's original form may become elongated. In these cases, the blood may have a tail this shows directionality. In order to find the angle of impact investigators measure the length and width of the blood droplet and use the formula $$sin(A)=width/length $$. The (A) representing angle of impact.

Impact Spatter
Impact spatter is the most common bloodstain pattern type in a crime scene. It occurs when an object hits a source of blood. In impact blood spatter patterns, blood is often circular and not elongated. There are two types of impact spatter. Back spatter and forward spatter. Back spatter occurs when the blood is projected back at the attacker while forward spatter is the blood that exits directly from the victims wound and projects onto nearby surfaces. The speed of the weapon used in the attack can cause changes in the size of blood spatter. The speed of the attack is classified into high, medium and low velocity attacks. High-velocity spatter (eg. gun shot wounds) create small sized droplets. High-velocity spatter usually occur between 100 feet/second and create blood droplets sized 1 millimeter or less. Medium-velocity spatter (eg. blunt force trauma) is often made with a weapon and can create cast-off patterns. They are often made at between 5 to 25 feet/second the blood droplets ranging from 1-4 millimeters in length. Low-velocity spatters are usually created just as a result of blood dripping from the individual (eg. gravity). Cast-off patterns are associated with impact spatter, these patterns are created when the object that is used in the attack is swung and the blood on the object is swung onto a nearby surface. By looking at the bloodstains the cast-off patterns can determine the direction in which the weapon was swung and the speed. In these cases, the length and the shape of the blood stain patterns can help determine the speed at which the object was swung. These patterns create elongated or elliptical shapes in blood when it hits the surface of an object. In 1895, Dr. Eduard Piotrowski's experiment showed that these patterns are often created after the second hit using the weapon.