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Blood Stain Pattern Analysis

Essay by   •  February 14, 2011  •  Research Paper  •  1,792 Words (8 Pages)  •  2,451 Views

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A nice young female is quietly walking back to her apartment late in the night, when she feels someone watching her. She quickly whips around to find that she is staring in the pure darkness. Nothing is there, she thinks to herself, but she can still feel the pure eeriness of someone watching her. She quickens her pace to make it to her apartment safely, but when she is about to be safely behind a locked door, something comes crashing down on her head. Blood goes splattering everywhere.

The criminal investigators come in the next morning to investigate what happened to this innocent lady. They put all their knowledge together and decide to try to solve this case by using what? Bloodstain Pattern Analysis!

Blood, the red liquid that is pumped through the arteries and is made up of many different cells, is forced out of the body in accidents and crimes. Each specie has different consistency of blood. Scientist's results are based on Homo sapiens blood. If they were to use animal blood the results would never come to be the same.

When thinking of bloodstain pattern analysis, one probably thinks, "Hmmm must be some complicated forensic science technology!" Actually, it is not; forensic scientists have used it since the 1890's. Bloodstain pattern analysis has been around for as long as fingerprinting has been used as a means to identify criminals. Hans Gross, in his 1892 papers, "Criminal Investigations," described bloodstains found at crime scenes and that the direction of the bloodstains could be determined by the shape of the bloodstain.

Balthazard, a French criminal analyst, found that the angle a bloodstain stuck the surface could be determined by dividing the width of a bloodstain by the length. This helped in determining the location from which the bloodstain came from. Eventually, they put this worked under the category of forensic science.

In defining bloodstain pattern analysis, some might say, "Show what happened at the crime scene through bloodstains, and there it is bloodstain pattern analysis." Technically that is incorrect, but basically that is what it is. According to the book Blood Stain Analysis by Terry L. Laber and Barton P. Epstein, it is the reconstructing of events causing the bloodstain patterns to be found.

In a crime involving bloodshed, a multitude of information can be gathered from using bloodstain pattern analysis. All of the following things can be learned using this forensic science: the location and orientation of the people and objects at the time the incident occurred, the movements of the person or object during the bloodshed, the place where the blood originated, the number of impacts and the event in which it took place, whether or not the suspect was bleeding, the position of the victim, and if a struggle took place in the event. When crimes happen with no witnesses, the forensic evidence at the scene becomes the most important to true witness of all. Forensics scientists use this technology to prove what happened at the scene. An important rule is the smaller the droplets of blood, the greater the force that made it. Also, air resistance affects smaller droplets of blood

According to scientists, there are five main bloodstain patterns to look for

* The impact pattern is the result of blood from a blow and hard impact.

* Then there is a cast off pattern, which is a result of blood being flung from an object in motion

* The gunshot pattern is a result from a gunshot

* There is the projected patter, which is a result from loss of large amounts of blood, such as bleeding from a main artery

* And last of all, the transfer patter, which is a pattern, which is a pattern when a non-bloody object comes in contact with a bloody object.

Blood is a very uniform material from the aerodynamic standpoint. Blood's ability to reproduce specific patterns is not affected significantly by sex, age, or diseases that the person bleeding might have. Since blood is shed from a body at constant temperature and is exposed to an external environment for such a short time, atmospheric temperature, pressure and humidity usually have no measurable effect on blood's behavior. Alcohol and drug used will also not affect bloodstains.

During the search for stains, in some cases investigators find it extremely difficult to find blood. When they are trained, they are given pointers on how to find them. A dried, but somewhat fresh bloodstain generally has a reddish-brown color and is glossy in contrast to, for example, it looks like a rust stain. In a very thin layer, the color might happen to be grayish-green. The gloss disappears slowly under the conditions of heat, exhaust, sunlight, wind, and weather, or as the result of trying to wash it away, the color then finally becomes gray. Bloodstains can, however, be other colors from red to brown to black, or they may appear green, blue, or grayish-white. The color and also the time taken preserve the pattern depend upon the surface it is on; the change is quicker on metal surfaces and slower on textiles. With some types of cloth, the blood soaks into the threads. Surface gloss is often less marked on the fabric. Bloodstains on wallpaper may show surprising colors because the blood is taking up color from the paper, or soaking in its print. Certain other stains made up of pigments, rust, tobacco, snuff, urine, feces, and other materials can be easily confused with bloodstains. In searching for bloodstains, marks should not be classified according to color and character since a stain that appears to stray from the normal character of a bloodstain may be composed of blood; instead one that resembles blood may be composed of some other substance.

Since blood evidence at a crime scene can provide clues that might solve the case, it is important to document, collect, and preserve this type of evidence. Surgical gloves, ventilation masks, body suit, and according to the situation, precaution goggles, should all be worn when working with blood evidence. Smoking, eating, or drinking these areas should not be permitted. When documenting bloodstains, a description

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