Blood pattern analysis.pptx

This presentation is a brief about the analysis of blood patterns present at crime scene.

1. PRESENTATION ON BLOOD SPATTER PATTERN ANALYSIS DEPARTMENT OF FORENSIC SCIENCE [SAM HIGGINBOTTOM UNIVERSITY OF AGRICULTURE, TECHNOLOGY & SCIENCES] Formerly ALLAHABAD AGRICULTURAL INSTITUTE PRYAGRAJ, INDIA SUBMITTED TO- SUBMITTED BY- Dr. Vaibhav Saran Sir PALLAVI KUMARI

2. BLOOD SPATTER PATTERN ANALYSIS

3. CONTENT INTRODUCTION AND BRIEF HISTORY 2.CLASSIFICATION OF BLOODSTAIN PATTERNS 3.BPA-HOW IT IS DONE? 4.CONCLUSION

4. INTRODUCTION Bloodstain pattern analysis or BPA is the interpretation of bloodstains at crime scenes in order to recreate actions that caused the bloodshed. Bloodstain pattern analysis (BPA) is an aspect of many forensic investigations, particularly those involving violence. It can help to determine the facts regarding an incident, the events that occurred throughout and can be supplemented by DNA analysis. BPA involves the examination of the number, pattern, size, shape, and location of bloodstains.

5. Blood stain created from the application of force to the area where the blood originated. The most important uses of bloodstain pattern analysis include: The reconstruction of the events of a crime or accident. To corroborate or refute statements of witness, victim or suspect. To bring about some certainty in cases where there is doubt as to involvement in a crime. For the identification of areas with high likelihood of offender movement for the prioritization of DNA samples. To differentiate between homicides, suicides and accidents.

6. Questioned to be answered… Did a crime occur is? Homicide or suicide? Homicide or accident? What kind of weapons was used? How many blows to the victim? How did victim react? What did the victim do after the suspect left the scene?

7. HISTORY OF BPA This field in Forensic Science became very much recognized during the. late nineteenth century. Blood being the most frequently encountered physical evidences in variety of crime scenes has raised awareness as to what could be interpret from it. Eduard Piotrowski is considered the earliest known person to study on blood spatters (1895). In the case of State of Ohio vs. Samuel Sheppard, an affidavit concerning evidence of blood spatters was submitted to the court by Paul Kirk. He showed the position of the victim and assailant (culprit) as well as showing that the assailant struck the victim with his left hand.

8. BLOOD In order to interpret bloodstains, we must know the basic principles of blood. Blood has both liquid (plasma) and solid parts(corpuscles). Blood is in liquid state inside the body as well as outside but only for a short period of time. Blood when outside the body begins to clot except from persons who suffer from hemophilia . The presence of blood clots can indicate that the attack was prolonged.

9. Blood is a fluid that makes up approximately 8% of the weight of a human body. Females have approximately 4-5 litres while males have between 5-6 litres. Blood is made up of cells (red blood cells and white blood cells) plus platelets in a yellowish liquid called plasma. Plasma contains gases (oxygen, carbon dioxide) and molecules such as proteins, fats and carbohydrates (sugars).

10. CLASSIFICATION OF BLOODSTAIN PATTERNS Bloodstain classification is very significant to investigators and analysts since it can yield information about the position before and after death, the type of force applied to cause the bloodstain, the direction from where the blood spatter came from and the type of weapon used on the victim. Also point of origin and directionality can be interpreted which will be discussed later. Classification is done based on- Velocity of the blood. Shape of blood.

11. Factors that affect bloodstain shape Force applied to the blood Surface characteristics Distance from surface Angle of impact Volume of blood Movement

12. Based on velocity bloodstains are classified into Low velocity stains Medium velocity stains High velocity stains Low velocity High velocity

13. Low velocity bloodstains is caused by blood dripping. For example, nose bleed or blood dripping from a bludgeoned knife. The force of the blood hitting the surface is 5 feet per second or less. The bloods diameter is large as 4 to 8 mm.

14. Medium velocity bloodstain is caused by beating with a blunt object like beating a person with a baseball bat. The force of the blood spatter is between 5 and 100 feet per second. The diameter of the blood spatter is smaller than that of low velocity blood spatter. They even appear as a spray.

15. High velocity spatter is caused by mainly gunshots. It can also be caused by other objects if enough force is exerted. The force of the blood spatter is more than 100 feet per second. This causes the spatter to appear like a fine spray. The droplet is less than 1 mm.

16. Bloodstains are classified into: 1. Passive 2.Transfer 3.Projected Passive bloodstains are due to the effect of the gravitational force. They are in the form of: Pools Drops Drips Clots

17. 2. Transfer stains are a result due to result of direct contact between the target surface and the blood source. It can be in the form of: Smears or swipe Contact bleeding Smudge Wipes

18. Cast off spatter(projected)- Gunshot spatter includes back spatter and forward spatter associated with gunshot wounds. These are mainly important in reconstruction of shooting incidents. Back spatter are large and few droplets whereas forward spatter are a fine mist. Blood spatter is a result due to the force other than gravity, acting on the blood source. It can be in the form of : Impact spatter(mainly gunshot spatter) Arterial spurt Expirated spurt

19. BPA (HOW IT IS DONE?) BPA starts with first documentation of the bloodstains. This is done with note taking, sketches, photography and sometimes videography is employed. Collection of articles that are transportable is done with standard guidelines and precautions and BPA analysis is conducted in the lab on such bloodstained items. Bloodstains found on walls and other immovable items are documented and the BPA procedure is conducted at the crime scene itself and then observations are recorded and opinions are formed by the BPA analyst.

20. BPA analysis is divided into 2 phases: Physical examination Reconstruction Physical examination involves identifying the stain pattern through its shape , size and location and thus , determining cause for the formation of the pattern. Here analysts need to be able to categorize the bloodstain thus therefore aid in determining the velocity at which the stain traveled and the amount of force acting on it giving an interpretation to what mechanisms may have caused them. In the given image interpretation that it is a cast off spatter shows that blood could have been projected from a swinging or flinged object.

21. Reconstruction involves methods that are used to answer certain questions such as: Distance between blood source and its impact? The locations of the culprit and victim relative to each other? The type of crime that occurred? Where is the person bleeding from? Did the bleeding come from the victim or the culprit? Were there any other interventions? Note: Always first document and collect to perform presumptive tests on the stains before the BPA analysis .

22. ANGLE OF IMPACT It is the angle at which the bloodstain strikes the target surface. In order to determine the angle of impact the width and length of the stain must be known. In order to reconstruct such events analysts have to determine the area of convergence and the area of origin. In order to determine the area of convergence(the starting point of bloodshed) angle of impact must be known. For example , if the width and length of the stain are same then through the given formula(from the image) we find out that the angle is 90 degrees indicating that the bloodstain fell vertically.

23. AREA OF CONVERGENCE: Area of convergence gives us the determination of where the bloodshed originated from whereas area of origin uses similar techniques that were used in determining area of convergence but gives us a three dimensional interpretation thus telling us about the positions of the victim and the culprit during the time of the bloodshed cause. A set of stains with distinct directionality are chosen where straight lines are drawn along their long axes and these straight lines slowly intersect at a common point which is the point or area of convergence.

24. AREA OF ORIGIN: After the determination of the area of convergence strings are attached to the stains selected for the area of convergence calculation and then, by using a protractor the strings are directed along the angle of impacts of those stains to a support system where the other end of each of the strings used is attached to that system(like a wall or a table). This complex time consuming procedure indicates where the victim was located at the time of the event. In the given image is the model of an area of origin in a crime scene indicating that the victim was probably standing near the table during the blood shedding event.

25. CONCLUSION BPA does not recreate incidents of the entire scenario of the crime that has taken place. It mainly supports findings of other forensic disciplines used in the case. For example, BPA may show that the statement made by the suspect about the victims suicide act is false(on interpreting a void pattern). Instead, it showed that it was a homicide. However it does not tell the age of the victim, whether the victim was under the influence of a drug or whether he was in a delusional state.

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