directionality angle of impact point of origin This information can then be used to determine the position of the body when the injury occurred. Blood Spatter Calculations Blood spatter occurs when something that contains blood is hit forcefully. The impact creates a splatter type stain that can then be analyzed to determine
What is the directionality of a bloodstain pattern?
The resulting bloodstain's shape will indicate the direction of travel for that stain and thus, the origin of the drop of blood. The “tail” or wave castoff of the bloodstain generally points to the direction of travel of the blood drop. The direction of travel and the angle of impact are referred to as the directionality of a bloodstain pattern.
How is the supposed trajectory of a bloodstain determined?
The supposed trajectory is determined based on the spread of blood spatter to determine the two-dimensional point of convergence. A line is drawn that follows the direction of each bloodstain.
What is the purpose of Blood Stain pattern analysis?
Bloodstain pattern analysis seeks to define the facts surrounding an investigation by the use of the physical nature of bloodstains. Bloodstain pattern analysis is the use of the size, shape, and distribution patterns of the bloodstains found at a crime scene to reconstruct the bloodshed event (s).
How are bloodstains used to determine where the impact occurred?
Therefore, at a crime scene when impacted bloodstains are found and after documentation, those bloodstains can be used to determine where the impact occurred using directionality of the individual stains in the overall pattern as part of reconstruction activities.
What is directionality in blood spatter?
Directionality -- The directionality of a bloodstain or pattern which indicates the direction the blood was traveling when it impacted the target surface. Directionality of a blood drop's flight can usually be established from the geometric shape of its bloodstain.
What is directionality in forensic science?
directionality angle. the angle between the long axis of a bloodstain and a predetermined line on the plane of the target surface that represents 0 degrees.
How does angle of impact affect blood spatter?
angle of impact = arcsin (stain width/stain length) Blood droplets elongate the higher the angle from which they strike the surface. The greater the difference between the width and length, the sharper the angle of impact [source: Dutelle].
How can an investigator tell the direction of travel of blood from the shape of a bloodstain?
An investigator may discern the direction of travel of blood that struck an object by studying the stain's shape. As a stain becomes more elliptical, its direction becomes more discernible because the pointed end of a bloodstain faces its direction of travel.
What is the meaning of directionality?
Definitions of directionality. the property of being directional or maintaining a direction. “the directionality of written English is from left to right” type of: spatial property, spatiality. any property relating to or occupying space.
What component of the blood spatter indicates the direction of spray?
What component of the blood spatter indicates the direction of spray? The head of the bloodstain.
Why is angle of impact important?
By measuring the width and length of the stain, the angle of impact can be calculated, helping investigators determine the actions that may have taken place at the scene. As the angle of impact changes, so does the appearance of the resulting stain.
How do height and angle affect blood splatter?
Specifically, it was to determine if: a) the greater the height from which the blood is dropped the bigger the size of the spatter will be and b) the steeper the angle from which the blood is dropped the more of an ellipse shape spatter will result.
What does the angle of impact determine?
In forensic science, the angle of impact is the angle at which a blood droplet impacts a surface. By definition, it is an acute (or right) angle (varying from 0° to 90° ). Knowing the angle of impact, detectives can partially reconstruct a crime scene by drawing "strings" from the spatter to an origin area.
How will you determine the directionality of bloodstains discuss briefly?
The “tail” or wave castoff of the bloodstain generally points to the direction of travel of the blood drop. The direction of travel and the angle of impact are referred to as the directionality of a bloodstain pattern. The directionality of a bloodstain will be used for reconstructing where the bloodshed occurred.
What does an analyst have to measure to determine the angle of the blood spatter and the position of the victim?
Then, he or she uses a protractor on the level line in the area where the strings converge to determine the angle of flight for each spatter. If the spatters are mostly on a wall, the analyst can measure the distance from the area of convergence to the wall to find out where the victim was located.
Why is it important to look at the surface that the blood was dropped on?
Too much blood can disguise spatter or make stain patterns unrecognizable. Conversely, too little blood, just one or two drops, will likely yield little or no useable information. Stains that overlap or come from multiple sources present challenges to analysts, but often reveal valuable details about the crime.
What are the 4 types of evidence in forensics?
There are four types evidence by which facts can be proven or disproven at trial which include:Real evidence;Demonstrative evidence;Documentary evidence; and.Testimonial evidence.
What are 5 examples of forensic evidence?
6 Major Types Of Forensics/ CSI Evidence Presented At TrialFinger Print Analysis. Along with DNA, fingerprints are a main identifier for who we are. ... Forensic DNA Analysis. ... Handwriting Exemplars. ... Blood Splatter Analysis. ... Forensic Pathology. ... Ballistics.
What are the five major types of trace evidence?
Fibers, hair, soil, wood, gunshot residue and pollen are only a few examples of trace evidence that may be transferred between people, objects or the environment during a crime. Investigators can potentially link a suspect and a victim to a mutual location through trace evidence.
What are the two types of associative evidence?
Two types of associative evidence are identi- fied: that with class characteristics and that with individual characteristics. Associative evidence that has class characteristics can be classified only as belonging to a certain class of objects; such an item may be excluded as belonging to other classes of objects.
How long did the three highway patrolmen have to train to do blood stain analysis?
Circuit Judge John Beger wrote that the blood evidence as presented at the trial was weakened by the fact that the three highway patrolmen who had led the bloodstain analysis had only 72 hours of training between them. “It was the key forensic evidence that they claimed,” says Jennings’ attorney, Robert Ramsey.
Which end of a stain would be closest to the origin of the blood?
For example, if the stain is in the shape of a teardrop, the rounded end of the drop would be closest to the origin of the blood, whereas the pointed end would face the direction the blood was traveling when it struck the surface where it landed.
Can you practice blood stain pattern without a degree?
As of right now, there is no universal standard, and some bloodstain pattern experts practice without college degrees. That’s one of many factors that led the National Academy of Sciences to critique the way BPA has been haphazardly applied in criminal cases in a 2009 report. Sometimes, the lack of training is extreme.
Diagnosis
- Many factors will influence the size and shape of a bloodstain once the drop reaches a target surface. A falling drop of blood when it impacts a surface will generally produce circular shaped patterns. The diameter of a bloodstain will increase as the distance that the blood drop falls increases until the acceleration of the drop remains constant and terminal velocity is reached. F…
Appearance
- The texture of the target surface upon which a drop of blood falls affects the size and shape of the bloodstain pattern. Hard, nonporous surfaces will produce circular stain patterns that have smooth edges but softer, porous surfaces will produce spatter stains that are scalloped or have rough edges. See Figure 7.3. The resulting shape of a bloodstain is changed when the angle at w…
Investigation
- Blood trails are frequently found at crime scenes. Careful examination and analysis of the trail pattern will provide information about direction of travel and the relative traveling speed of the bleeding sourcethe reconstruction. As the speed of the bleeding source in a horizontal motion is increased, the more elongated shape of the individual sta...
Formation
- Contact patterns can be formed due to folded bloody surfaces. Two similar bloody imprints may result from the same object, or one image from the other bloody image, hence a butterfly or mirror image of the original stain is created. Contact patterns can often be created though dynamic motions. When an unstained object moves through a bloody surface or an existing bloodstain th…
Effects
- Impacted bloodstain patterns have received more energy (force) than gravity and are called impacted bloodstains. The force added to the blood causes the blood to break into smaller sized spheres or spatters. The smaller sized blood spatters are relative to the amount of force or energy involved. The greater the added force then smaller the size of the resulting spatter. Though the s…
Types
- This spatter behavior will be used to determine the origin of the impact or where bloodshed occurred. Generally, impacted blood spatter falls into two types: (1) Medium-force and (2) High-force impact spatter. See Figure 7.8. Medium force impact spatter is produced by a force associated with beatings and blunt or sharp force trauma. The size of this spatter is much small…
Causes
- When bloodshed occurs it is not uncommon for that bleeding source to continue to bleed-out. This bleeding will cause blood to drip into an increasing pool of blood that will cause secondary spatters to be produced. These secondary spatters basically bounce and make for smaller stains around the pool of blood. If sufficient blood drips and time passes, a blood pool is created that o…
Pathophysiology
- When there is a sudden release of an increased quantity of blood from a severed artery the resulting stain is called a projected bloodstain pattern. This bloodstain pattern is commonly associated with major injuries with open wounds usually to an artery. This pattern has sharp, spinous edges and can easily show movement. For this reason these patterns are useful for rec…
Mechanism
- A two-step process determines the point of origin of bloodshed from an impact mechanism. First, representative samples of individual blood spatter in the impact pattern are selected. Their direction of travel is marked by placing a line through the center of each stain and drawn back to the direction of their origin. The lines will converge in an area called the point of convergence. S…