Bloodstain pattern analysis

Geberth, Practical Homicide Investigation Reprint: Law and Order, Vol. The trails of blood in a crime scene or castoff blood patterns are reasonably straightforward and understandable.

Bloodstain pattern analysis

In the past analysts have used a variety of instruments. Methods currently used include: Viewing loupe with an embedded scale in 0. The analyst then uses a scientific calculator or spreadsheet to complete the angle calculations.

Bloodstain pattern analysis

Bloodstain Pattern Analysis BPA software that superimposes an ellipse over a scaled close-up image of an individual bloodstain, then automatically calculates the angles of impact.

Using BPA software such as HemoSpat produces Bloodstain pattern analysis very accurate result that is measurable and reproducible. The tangential flight path of individual droplets can be determined by using the angle of impact and the offset angle of the resulting bloodstain.

For the purpose of the point of convergence, only the top view of the flight paths is required. Note that this is a two-dimensional Bloodstain pattern analysis and not a three-dimensional 3D intersection.

The point of convergence is the intersection of two bloodstain paths, where the stains come from opposite sides of the impact pattern. Instead of using a top-down view, they used a front view.

The area of origin includes the area of convergence with a third dimension in the z direction. Since the z-axis is perpendicular to the floor, the area of origin has three dimensions and is a volume The term point of origin has also been accepted to mean the same thing.

However, it has been argued, there are problems associated to this term. First, a blood source is not a point source.

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To produce a point source the mechanism would have to be fixed in three-dimensional space and have an aperture where only a single blood droplet is released at a time, with enough energy to create a pattern.

This does not seem likely. Second, bodies are dynamic. Aside from the victim physically moving, skin is elastic and bones break. Once a force is applied to the body there will be an equal and opposite reaction to the force applied by the aggressor Newton's third law of motion. Part of the force will move the blood source, even a millimetre, and change the origin while it is still producing blood.

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So the source becomes contained in a three-dimensional volume, or region. As with the area of convergence, the area of origin can be calculated by using BPA software.

There are other longer, mathematical methods of determining the area or origin, one of which is the tangential method. Point Area of Origin - The common point area in three-dimensional space to which the trajectories of several blood drops can be retraced.

The most basic and longest applied technique is the string method. A blood spatter analyst positions their protractor at the location of the blood stain and projects a string at the angle of impact in the direction of the point or area of convergence.

This will predict a general origin of the blood loss. Another technique applicable is the trigonometric method, which is fairly similar to the string method.

Since we know the point of convergence, we can measure the distance from the blood stain to that point. With this measurement along with the angle of impact, we can use basic trigonometric rules to solve for where in space the origin of blood shed is.

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By taking the tangent of the angle of impact and multiplying by the distance from the point of convergence, we can find the approximate height of the origin. Forensic photography Crime scene photography has some unique requirements.

When there is a bloodletting scene, the basics are still required but special attention must be given to the bloodstains. Each method has its pros and cons. Often the scene is documented using multiple methods. Videography has been included here because it follows the same principles and provides crime scene images.

There are three types of crime scene photos: This type of image provides anyone who has not been in the scene a good overall layout. In the case of a bloodletting scene, the mid-range image could capture a single bloodstain pattern.

Close-up — images taken with a macro lens giving the greatest amount of detail. Many times an analyst cannot attend a bloodletting scene, and must work from the crime scene images and notes of the person who attended.

An appropriate sized scale should be in overall, mid-range, and close-up images.

Bloodstain pattern analysis

For overall images the scales should be parallel and perpendicular to the floor. This provides the analyst, and anyone else who looks at the images, a proper perspective on what they are observing.The mission of SWGSTAIN is to promote and enhance the development of quality forensic bloodstain pattern analysis (BPA) practices through the collaborative efforts of government forensic laboratories, law enforcement, private industry, and academia.

Upcoming Training Opportunities. Register for a Course. Hosting a Course. Hosting & Attending a Course FAQ. Forensic Pieces Calendar. View our Gallery. When violent crimes are committed, it is not unusual for the participants to be injured. If these injuries are accompanied by blood flow, distinctive bloodstain patterns may result that can be used to provide investigative information about the activities which occurred during the commission of the.

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Discuss, share and compare stain pattern analysis methods, protocols, and research for the enhancement of forensic bloodstain pattern analysis (BPA) techniques.

2. Design and encourage the implementation by practitioners of a quality assurance program in bloodstain pattern analysis and to advise the forensic bloodstain pattern analysis.

How Bloodstain Pattern Analysis Works | HowStuffWorks