Blood+Spatter+Analysis

Forensic investigators use Blood Spatter Analysis to learn a great deal about a crime. From the crime scene, they can determine what happened, help solve the crime and determine whether or not the crime was even committed. Blood is important to crime scenes because of the way it moves and clots. Knowing how it operates inside and outside the body enables investigators to get to the bottom of how the bloodstain got there. For example, the shape and location of the bloodstains can provide clues about where the victim and the suspect where when the crime took place and where they went afterwards. Bloodstains are helpful as they can provide a lot of information such as:
 * The origin of the bloodstains [[image:patterns0304.jpg width="427" align="right" caption="Left: Passive bloodstains. Right: Bloody shoe print transfer patterns"]]
 * The type of instrument that caused the bloodstains
 * The direction from which an object struck the victim.
 * The relative position of the victim, the assailant and the bystanders.
 * The locations and movements of the victims and assailants during the attack.
 * The number of blows or gunshots the victim received
 * The truthfulness of any suspects or witnesses.
 * = Contents ||
 * # Overview
 * 1) Job Description
 * 2) Type of Instruments Used
 * 3) Application in Investigations
 * 4) Case involving BSA
 * 5) Informational Videos
 * 6) Bibliography ||

Job Description
The primary purpose of a Blood Spatter Analyst also known as a Bloodstain Pattern Analyst is to collect physical evidence. They specifically examine the location and shape of blood drops, stains, puddles and pools and are required to have backgrounds in scientific studies. As a Blood Spatter Analyst, you must have specific knowledge in subject areas such as mathematics, physics, chemistry and biology. Furthermore, Blood Spatter Analysts must undergo specific training and attend numerous work shops pertaining to Blood Spatter Analysis. Blood Spatter Analysts are also required to continually update themselves and their knowledge as well as skills once they have settled in their career.

There is a high demand for bloodstain pattern analysts around the world and with the growing amount of technological and scientific advances, this demand is potentially increasing. The usual earnings of a Bloodstain Pattern Analyst can range from $30,000 to $83,000 per annum and the mean salary is around $55,000.

**Cutting instrument and evidence packaging **
Whenever possible, analysts or crime scene investigators try to collect the evidence intact. This may require removing a section of a wall or carpeting, furniture, or other large objects from the crime scene and sending them to the laboratory for analysis.Analysts or investigators will also soak up pooled blood, or swab small samples of dried blood in order to determine if it is human blood and then develop a DNA profile.

The most frequently used method of capturing bloodstains is high-resolution photography. A scale or ruler is placed next to the bloodstain to provide accurate measurement and photos are taken from every angle. Video and sketches of the scene and the blood stains is often used to provide perspective and further documentation. This is commonly done even if stained materials or objects are collected intact.
 * High-quality cameras (still and video), scale or ruler and sketching materials **

Creating a DNA profile becomes critical when there are multiple victims. DNA profiling may also indicate whether the perpetrator was injured during the attack, as in the case of two DNA profiles found at a scene with only one known victim.
 * Blood-analyzing equipment **


 * <span style="font-family: Arial,Helvetica,sans-serif;">Elastic strings and protractor **
 * <span style="font-family: Arial,Helvetica,sans-serif;">Mathematical equations (tangent trigonometric function) **
 * <span style="font-family: Arial,Helvetica,sans-serif;">Computer software programs such as BackTrack™ or Hemospat **

<span style="font-family: Arial,Helvetica,sans-serif; line-height: 1.5;">To help reconstruct events that caused bloodshed, analysts use the direction and angle of the spatter to establish the areas of convergence (the starting point of the bloodshed) and origin (the estimation of where the victim and suspect were in relation to each other when bloodshed occurred). <span style="font-family: Arial,Helvetica,sans-serif;">To find the area of convergence, investigators typically use string to create straight lines through the long axis of individual drops, following the angle of impact along a flat plane, for instance the floor or wall where the drops are found. Following the lines to where they intersect shows investigators where the victim was located when the drops were created. <span style="font-family: Arial,Helvetica,sans-serif;">To find the area of origin, investigators use a similar method but also include the height calculations. This creates a 3-D estimate of the victim’s location when the drops occurred. For example, if the area of origin is determined to be only two feet above the area of convergence on the floor, the analyst may presume the victim was either lying or sitting on the floor. If it is five feet above the convergence, the victim may have been standing. This analysis can be done using strings and a protractor, mathematical calculations or computer models.

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 140%;">Application in Investigations
<span style="font-family: Arial,Helvetica,sans-serif;">The police and investigators often use blood spatter analysis to help determine who committed the crime and how he did it. Blood is primarily made of water and as such, it behaves much like water and therefore must obey the laws of motion and gravity. The blood droplets are round when travelling through the air but deform into various shapes and patterns when they land on a hard surface. The size and shape of these droplets tells detectives about how the person lost the blood. From blood spatter, detectives can determine what type of weapon was used, how many times a person was hit with it, if the bad guy was right or left handed, the position of the victim and how they moved during the attack, how long ago the crime was committed, and how long the person lived after their injuries. <span style="font-family: Arial,Helvetica,sans-serif;">The size of the bloodstain depends on how much blood was lost. If a lot of blood was lost, the blood droplets will be quite large. Detectives use this information when determining whether a person died or not. <span style="font-family: Arial,Helvetica,sans-serif;">The shape of the blood stain depends on the angle of the blood when it hit the surface and the speed at which the blood drop was travelling. A droplet that has fallen vertically will be more round than a droplet that has hit the surface at an angle which will be oblong shaped. <span style="font-family: Arial,Helvetica,sans-serif;">Drops that hit at an angle form a tail which typically points in the direction that the drop traveled. If you measure the width and length of the drop, then divide the width by the length, you can determine at what angle the blood struck the surface. If this ratio comes out to be .5 then the blood struck the surface at a 30-degree angle. If the ratio comes out to .25, the droplet struck the surface at a 14-degree angle. <span style="font-family: Arial,Helvetica,sans-serif;">Detectives also look at how dry the blood is. Blood begins to dry and clot within 15 minutes (depending on factors such as heat and humidity). The outer edges of droplets tend to dry first and a completely dry droplet may leave a dark ring. How dry the blood is gives the detectives an idea of how long ago the attack happened. <span style="font-family: Arial,Helvetica,sans-serif;">Detectives look at other factors too such as whether or not the blood contains bone or tissues matter (which indicate a high impact splatter). They look for voids or blank spots which may indicate something else (a person maybe) absorbed the blood spatter and then left.

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 140%;">The Murder of Diane and Alan Scott Johnson
On September 2, 2003, Alan Scott Johnson and Diane Johnson were shot to death in their Bellevue, Idaho home. Their daughter, Sarah Johnson, was convicted guilty of their murder. Sarah was 16 years old at the time. The prosecutor stated that her motive was her parents' prohibiting her from dating a 19-year-old.

According to the prosecutor’s description, Sarah Johnson took a Winchester rifle at approximately 6:20 am and walked into her parents' bedroom, shot her sleeping mother in the head. She then walked into the bathroom and shot her father in the chest, right above the heart, while he was showering. DNA evidence and gun residue were found on a discarded bathrobe and a latex glove that police found in the garbage can.The case was trialed in front of an Ada County, Idaho jury on March 16, 20 05. In court, the defense claimed that the close-range shots that killed Diane Johnson would have projected a significant amount of blood at the shooter, who was standing no more than a foot away from the victim. Furthermore, when investigators analyzed the pajamas Sarah Johnson was wearing that morning, they found no traces of her parents' blood or DNA on her clothing or her person. They also pointed out that no blood was found on the tops of the socks she was wearing, although evid ence already has been established that her mother's blood was found on the bottoms of the socks. Police also found blood spatter on a pink bathrobe that Sarah said was hers. It was concluded that the misting pattern of the blood indicated that the shooter was wearing the robe, as previous witnesses had testified. However, Sarah's DNA, which was found in the robe, cannot be linked to the day of the shootings became a key argument in the defense's case. The defense attorney further disputed the state's contention that Diane Johnson's head was covered by the sheets and comforter when she was shot, which would explain the lack of blood on the defendant. On cross-examination, Blaine County prosecutor Jim Thomas attacked Howard's credentials and the scientific validity of his methods, and compared Howard's three-sentence analysis of the evidence to the 12-page report the state's blood spatter expert, Rod Englert produced. Johnson was found guilty of the murders of her parents by an Ada County, Idaho jury on March 16, 2005. She was sentenced to two concurrent life terms plus fifteen years for a firearm enhancement. The Idaho Supreme Court upheld her conviction.S arah Johnson now faces life in prison after Blaine County prosecutors chose not to seek the death penalty on two counts of first-degree murder -- which could have proved problematic against the execution of juveniles. When Sarah Johnson's charges came up, prosecutors chose not to seek the death penalty because the Supreme Court had recently ruled against executing mentally retarded convicts.

Informational Videos

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