14 December 2014
Blood and Guns The world of Forensic Scientist is an amazing and fascinating place. There are so many aspects that go into forensic science but in this paper we are only covering bloodstain spatter patterns. Bloodstain spatter patterns are not solely used to solve crimes but I do feel it is one of the most important. Bloodstains never lie.
A bullet is traveling at its fastest speed when it leaves the barrel of the gun. Bullets traveling after firing is said to be using kinetic energy. Kinetic energy is the energy the bullet has due to its motion from the firing pin striking the gun powder causing an explosion that forced the bullet to discharge from the barrel. Now this bullet possess kinetic energy and will do harm to anything lying within its targeted path. (Kinetic Energy website)
The kinetic energy given to bullets fried from rifles will be a higher velocity then that of a pistol or shot gun. Rifles barrels are longer and constructed to with stand more pressure and thus leading to a greater velocity of kinetic energy on a bullet (Warlow 67). Death can occur from firing a bullet straight up in the air. When the bullet is returning to the earth due to the gravitational pull it will pick up velocity. However the bullet can return either base or head side up (89).
Powders also have different burning rates for different guns. When you have a longer barrel your burning rate of powder will be longer but if your barrel is shorter then you will have a faster burning rate (Warlow 67). On today’s market most smokeless powder is made up of nitrocellulose and nitroglycerine. If it is a single base powder then it is made up of nitrocellulose. If it is a double base powder then it is a mixture of nitrocellulose and nitroglycerine. Nitrocellulose and nitroglycerine in their pure form are extremely volatile to use so they must be mixed with other compounds such as ether and alcohol then reduced in size to be used within a bullet. This mixture even in reduced size is still to explosive and needs stabilizers added. Stabilizers commonly used are diphenylamine and potassium sulfate (Warlow 67).
When you fire a gun not all of the powder will burn up and the powder left behind will leave a residue on your clothing or skin if you have fired the weapon or were standing close to a fired weapon. This residue will also be on your target if you are close to your target. This can help forensic scientist determine how far away from the target you were standing upon firing your weapon (Warlow 69-70). To determine if residue is on an individual forensic personal will use a scanning electron microscope (71-72).
Each gun barrel has what we like to call a signature. This means that when a bullet is fired from that gun it will leave behind striations unique to that weapon. This signature is actually made of imperfections with in the barrel or marks that occur over time. When examining a gun for a bullet striations match they will perform a test fire and this test can be performed in many ways. From shooting into a bullet proof case filled with gelatin material to shooting a bullet into water, either way you must fire the bullet into a material that will quickly and safely slow the bullets kinetic energy to avoid accidents within the forensic lab (Warlow 72-73).
We have internal and external ballistics. Internal ballistics is only concerned with the bullet while it remains in the barrel (Warlow 65). External ballistics deals with the bullet from the time it leaves the barrel until it hits its final target. External ballistics has much more ground to cover than internal. External ballistics deals with the bullets flight path, weather conditions that may affect the pathway of the bullet, and that basic law of gravity. Items that did not burn completely up upon the firing of the weapon will also be discharge and looked at under external ballistics. Sometime you have coal and wood pieces that will fly into your target and cause damage depending on how close you are standing (Warlow 81).
Depending on what the bullet hit will depend on the damage that is done. The bullet will so receive damage itself causing it to be deformed and sometime disintegrate depending on the target. Damage to the human body varies depending on where the bullet penetrates. Muscle will offer more resistance to the bullet versus fatty tissue or an organ such as the liver. If a bullet penetrates your lungs it will cause them to collapse. Bullets have also been known to bounce off a person’s ribs. Depending on what clothes you are wearing, like a heavy thick sheep skin jacket will have a tendency to help slow down the bullet but won’t stop it from penetrating the human body. There is no set rules of what will happen when you are shot. The closer the range to the intended target the more damage you will do. This is one reason suicide via gunshot wounds are so big (Warlow 109).
Upon arrival at a crime scene you will need to speak with the lead officer or lead crime scene investigator to find out what allegedly happened at the crime scene. There are certain precautions that are taken at crime scenes to preserve evidence. First you will have to wear protective gear including, hair net, shoe covers, plastic surgical gloves, suits and any other items that are required to prevent scene contamination. This gear will also help protect you against any health hazards that may be located in the crime scene such as blood or tissue contaminates. Before entering a crime scene be sure to look for protective plates that are put in place to preserve footprints left behind, and if you do not see any be sure to lay them. Before you can begin collecting evidence you must first make a complete sketch of the entire crime scene. Ensuring that you include where bodies are lying, bullets, spent cartridges, any weapons, blood splatter, and any other items deemed important. Photographs of the scene will be accomplished by the scene of crime officers before forensic investigators arrive, but forensic investigators will also take pictures. Evidence will be marked with numbered markers and photographed again. Any and all dimensions will be measured and recorded (Warlow 139-140).
Bloodstain pattern analysis is the study of the physical nature of bloodstains and from this study forensic investigators try to gain a picture of what took place at the crime scene. Blood spatter patterns at crime scenes is often referred to as static aftermath. In this “Dispersion, shape characteristics, volume pattern, the number and size of bloodstains and their relationship to the surrounding scene are part of this aftermath” (Bevel and Gardner 1).
Blood is a fluid that will react to an outside force like any other fluid will. “The cohesive forces of surfaces tension and viscosity, the various external forces (e.g. impact, accelerated motion, stream ejection) as well as gravity and air resistance will act together to produce similar results (patterns) under generally similar conditions” (Bevel & Gardner 1). What this means is when fluid is subjected to an outside force it will react in certain ways and these reactions can be reproduced so we can establish normal patterns of behavior of blood from this. These patterns of blood spatter can help investigators solve crimes or lead them to ask more questions. One important thing to remember about blood is that it runs the entire length of your body in just a minute (Ritichey Chromosomes).
We have many patterns that we look at called, impact, cast off, spurt and gush, drip and drip trails, pools and flows, blood into blood patterns, blow back, atomized blood, void and blood misting and lastly smears and pattern transfers. Now let’s briefly describe what each of these are (Bevel and Gardner 2).
For the impact pattern let’s imagine a juicy watermelon in an oval shape similar to a human head and you hit this water melon on one side with a bat. The watermelon would bust under the pressure of the hit and would spread out to the surrounding area from the point of impact. The juice and matter from the watermelon would leave impact patterns all around the point of origin. Since it was a direct impact it is typically that you measure a 3ft dimensional radius for this. Also forensic scientist would check for angle of impact and directionality to try and determine the height of the criminal. Most people when performing task with their hands will automatically use their dominate hand so in determining the directionality of the hit you can figure out the dominate hand of the criminal. Depending on the wound you can also draw a conclusion of the weapon used on the victim. If we see blood spatter on top of blood spatter this will help you determine the number of blows the victim has received and which blow actually killed the victim (Bevel and Gardner 2).
Continuing with the juicy watermelon example from above lets refer to the bat for this example. As you swing the bat back and forth hitting the watermelon there will be juice and pieces of the watermelon on the bat that will fly off with each swing and land on nearby objects or walls. This is referred to as cast off pattern. From this we can help to determine the amount of blows the victim received. This type of pattern will also help forensic scientist discover the directionality and angle of the blows which in turn will help determine where the criminal was standing (Bevel and Gardner 23).
Not let’s imagine that we are holding a water balloon and you poke that balloon with a safety pin creating a tiny hole. With all the pressure inside the balloon the water will shoot out of the balloon and leave a single wavy line pattern. This is what we call spurt and gust patterns. The reading explains that these patterns typically come from arterial or heart wounds, because these areas of your body have a higher pressure of blood pumping through them at one time and when this pressure is released the blood will rush out the first exit it finds (Bevel and Gardner 19).
Imagine running down a carpeted hallway with an open cup full of red Kool-Aid. You get a clear picture of the Kool-Aid splashing out of your cup leaving drops in a trail behind you. This is the same concept of drip and drip trails. After you reach the end of the hallway you will have left a long directional trail of red juice drops some will be larger and others will not be. From this we can determine where the crime scene started and what direction it moved forward (Bevel and Gardner 25).
For this next example of pooling let’s say you’re holding a plastic solo cup filled with red Kool-Aid and you stab the bottom of your cup with a knife. All your liquid will fall out onto the floor creating a puddle per say of Kool-Aid. According to the reading this puddle has no boundaries and will react with the flow of the room which is referred to as pooling and flow. The flow is determined by gravity, once it leaves the body. Flow can impact all blood spatter patterns. This mostly occurs from fatal wounds where the victim is left to bleed out on the spot (Bevel and Gardner 63-64).
Think about watching an artist throw black paint on a canvas and then he throws pink paint on top of the black paint. Well this is the same idea for blood into blood patterns. It is when blood is thrown on top blood and this type of pattern is more difficult for forensic scientist to analysis but not impossible. This is usually a result from multiple blows with a weapon or shots (Bevel and Gardner 20-21).
Let’s think back to the firearm discussion from earlier in this paper. We talked about how the closer you are to the target the more damage that will be done due to the kinetic energy being at its greatest velocity when the bullet leaves the barrel. Which in turn means damage will be greater to the human body the closer the gun is. From the reading we understand that at close range firing at a human target there will be what is referred to as blow back of blood, tissue and maybe small fragments of bone in the barrel of the gun. The closer you are the further up the barrel the blow back goes (Bevel and Gardner 21).
For this next example let’s think about Windex we are about to spray on a window which needs cleaned. You set your Windex bottle nozzle to mist and when you spray the bottle you get a somewhat round circle of tiny drops of Windex on the glass, well in blood spatter this is referred to as atomized blood and blood misting. Now in blood spatter it is not always in the shape of a circle and is usually created by some forced explosion. Example a shot gun wound, we have all seen this in the movies (Bevel and Gardner 21).
Imagine you are walking and you accidentally step into wet paint, as you walk the paint will transfer as you step on the floor in the pattern of the sole of your shoes. This concept is known as pattern transfer. (Bevel and Gardner 29) Whenever you spill thick pile of liquid on the counter and try to wipe it up leaving smears on the surface because you cannot quite soak it all up with one paper towel, this is called wipe which is a subcategory of smear. Smear has two categories and we just learned about wipe now let’s look at the one swipe. A good example of swipe would be after you spilled tomato juice on the floor and it started to dry and then you accidentally drag a pair of pants through it. The tomato juice will transfer to your pants leaving a streak or drag pattern in the tomato juice. (Bevel and Gardner 35)
The last and final pattern will discuss for blood spatter is void. A perfect example to describe this is an individual standing with his or her back against the wall with a firing squad standing in front. Now let’s say the guns are paint ball guns filled with red paint balls. The firing squad unleashes on the individual standing aginst the wall. When that individual walks away from the wall there will be a clean spot where they were standing and this is what we call a void. This means when investigating a crime scene that something was there and we must determine what it was (Bevel and Gardner 31-32).
All blood found at crime scenes will be processed in a lab to find its Deoxyribonucleic acid or as commonly known DNA. DNA is genetic material that created in each person and in reproduction it is referred to as chromosomes. And we get this DNA from both our parents. We all have 46 chromosomes or 23 pair’s altogether. During reproduction our cells containing chromosomes divide from 46 (known as diploid cells) to 23 (known as haploid cells). So when reproductions occur you will have the female egg and the male sperm both containing 23 chromosomes and when mixed they produce a baby with 46 chromosomes (Ritchey Chromosomes). DNA is specific to each individual meaning no one else will share that same exact DNA. This is important to the forensic scientist because if an individual was found guilty of another crime and served time their DNA will be found in the National DNA database on file. If one of your parents DNA is in the database and forensic scientist run your DNA through the system then your parents will come up flagged as having shared alleles. Alleles are the actual name of the genetic code for which your traits fall into. Example Windows peak hairline and the code would be W. Law enforcement will still be able to track you down when you commit a crime and your family members DNA is located within the DNA database (Ritchey Genetics).

Work Cited
Bevel, Tom, and Ross M. Gardner. Bloodstain Pattern Analysis: With an Introduction to Crime Scene Reconstruction. Boca Raton: CRC/Taylor & Francis, 2008. Print.
Warlow, T. A. Firearms, the Law and Forensic Ballistics. London: Taylor & Francis, 1996. Print.
"Kinetic Energy." Kinetic Energy. N.p., n.d. Web. 05 Nov. 2012. <http://hyperphysics.phy-astr.gsu.edu/hbase/ke.html>.
Ritchey, Mary. “Humans in the World of Biology.” Harrisburg Area community College. Introduction to Human Biology. George W. Leader, York. 20 Aug. 2012. Lecture.
Ritchey, Mary. “Chromosomes and Cell Division.” Harrisburg Area community College. Introduction to Human Biology. George W. Leader, York. 17 and 19 Sep. 2012. Lecture.
Ritchey, Mary. “Genetics.” Harrisburg Area community College. Introduction to Human Biology. George W. Leader, York. 24 Sep. 2012. Lecture.