Warning: Some material in this presentation and related videos may be considered graphic.

Transcription

1 Warning: Some material in this presentation and related videos may be considered graphic.

2

3 This is How Hollywood Does Blood Spatter Analysis:

4 The first step in analyzing blood: Making sure a substance is actually blood. There are several ways to do this. Investigators will first examine the crime scene to look for areas that may contain blood. The second step involves conducting a presumptive test to determine if the substance you found is actually blood.

5 Finding the blood: Method 1 Alternate Light Source: A high-intensity light or UV light helps to find traces of blood as well as other bodily fluids that are not visible under normal lighting conditions.

6 Luminol / Blue Star Used to locate traces of blood, even if it has been cleaned or removed. Spray a luminol solution throughout the area. Look for the reactions with the iron present in blood, which causes a blue luminescence. One problem is that other substances also react, such as some metals, paints, cleaning products, and plant materials. Another problem is that the chemical reaction can destroy other evidence in the crime scene. Luminol Reaction

7 Luminol on a crime scene sink: Wait until you see the next picture

8 Okay, its from the videogame Dead Space.

9 Fluorescein This chemical is also capable of detecting latent or old blood, similar to luminol. Ideal for fine stains or smears found throughout a crime scene. After the solution has been sprayed onto the area suspected to contain blood, a UV light and goggles are used to detect any illuminated areas. They will appear greenish-white if blood is present. It may also react to many of the same things as luminol (copper, ammonia, bleach, etc). Fluorescein Reaction in UV Light

10 LCV or Leuco Crystal Violet, is one type of chemical process that is used for blood enhancement. Using this test helps to make the blood evidence more visible so it can be photographed and analyzed.

11 Verifying that a substance is blood Blood Reagent Tests These tests, referred to as presumptive tests, are used to detect blood at crime scenes based upon the properties of hemoglobin in the blood. Further tests at the crime lab must be done to verify that it is human blood. Examples: Kastle-Meyer test (see next slide). HemaStix is a strip that has been coated with tetramethylbenzidine (TMB) and will produce a green or blue-green color with the presence of hemoglobin.

12 The Kastle-Meyer test Presumptive blood test, first described in The chemical indicator phenolphthalein is used to detect the possible presence of hemoglobin. It relies on the peroxidase-like activity of hemoglobin in blood to catalyze the oxidation of phenolphthalein which is initially colorless, and turns pink color in the presence of hemoglobin.

13

14 Blood Spatter Analysis is: More correctly called Bloodstain Pattern Analysis (BPA). One of several specialties in the field of forensic science, involves the study and analysis of bloodstains with the goal of helping investigators draw conclusions about the nature, timing and other details of the crime. Using bloodstains as evidence is not new; however, modern science has brought it to a higher level since the 1970s and '80s. BPA draws on the disciplines of biology, chemistry, mathematics and physics.

15 History Pitorowski wrote earliest reference to bloodstain pattern analysis Balthazard was first to use physical interpretations of stains Dr. Paul Kirk used bloodstain pattern interpretation as a defense witness in the Sam Shepherd case Professor Herbert MacDonnell promoted bloodstain pattern interpretation as a tool for modern criminalistics The International Association of Bloodstain Pattern Analysis was formed.

16 Basic Principles of Blood Spatter Blood drops form different shapes and sizes. Blood spatter analysis uses the shapes and sizes to reconstruct the crime scene.

17 Basic Principles of Blood Spatter A free falling drop of blood forms a sphere or ball. A spherical drop will break 1. When it strikes another object 2. When acted upon by some force

18 Formation of Blood Spatter:

19 What can an investigator learn from the analysis of a blood spatter? Type and velocity of weapon Number of blows Handedness of assailant (right or left-handed) Position and movements of the victim and assailant during and after the attack Which wounds were inflicted first Type of injuries How long ago the crime was committed Whether death was immediate or delayed

20 Blood Pattern Analysis The use of physics and math to interpret bloodstain patterns within a forensic setting May show: 1. Activity at scene 2. Number of blows 3. Position of victim and assailant 4. Whether death was immediate or delayed 5. Weapon characteristics

21 Bloodstain Pattern Analysis Terms Origin/Source The place from where the blood spatter came from or originated. Spatter Bloodstains created from the application of force to the area where the blood originated. Angle of Impact The angle at which a blood droplet strikes a surface.

22 Bloodstain Pattern Analysis Terms Parent Drop The droplet from which a satellite spatter originates. Satellite Spatters Small drops of blood that break of from the parent spatter when the blood droplet hits a surface. Spines The pointed edges of a stain that radiate out from the spatter; can help determine the direction from which the blood traveled. Satellite Spatters Spines Parent Drop

23 Velocity Speed applied in a specific direction. Certain blood patterns are created by blood moving at a specific speed. This speed affects the way the spatter looks.

24 Spatter size is dependent upon velocity Low velocity: Speed = about 5 ft/second. Usually 3 mm or greater in diameter. Indicates blood is dripping. Medium velocity: Speed = 6 25 ft/second. Between 1-3 mm in diameter. Usually indicates blunt trauma, sharp trauma or cast-off. High velocity: Speed = 100+ ft/second. Less than 1 mm in diameter. Indicating gunshot trauma, power tools, an object striking with extreme velocity (airplane prop) or an explosion. May be referred to as fly specks. Medium High

25 High Medium Low

26 There are 3 categories of spatter patterns: Passive Projected Transfer

27 Passive Bloodstains Formed by the force of gravity acting alone. Subdivided into: drops, drip patterns, pools & clots, and flows. Created by oozing from a wound dripping, or drops from an object (knife).

28 Drops and Drip Patterns Drops are single blood drops. When they strike a surface at 90º, the spatter created will be circular. When they strike at anything other than 90º, they become more oval. The oval shape becomes more exaggerated the farther you move away from 90º.

29 Pools & Clots, and Flow patterns Pooling bloodstains refer to the accumulation of blood on a particular surface, generally from prolonged bleeding from a wound or accumulation of arterial blood. Gravity has no pull on it, so it collects in one spot. Clots can be found in passive patterns when the blood coagulates and is added to, moved or disturbed. Flow occurs when a large amount of blood hits a vertical surface at one time. Gravity will pull excess blood to one point and cause it to run down the surface.

30 Horizontal Blood Flows

31 Satellite Spatter Caused by free falling drops of blood that fall onto a pre-existing drop. These drips are usually much larger than impact spatter. However, blood dripping into blood can create a spatter.

32 Projected Bloodstains Is created when an exposed blood source is subjected to an action or force greater than gravity. Blood pools due to internal activity (expirated blood) OR external force (stabbing, beating, gunshot). Subdivided in to the following types: arterial spurt/gush, cast off stains, expiratory blood blown out of the nose, mouth, or wound and impact spatter. Includes low, medium, or high impact spatters.

33 Impact Spatter The result of a forceful impact between an object and wet blood, causing the blood to break into smaller droplets. A greater force will typically produce smaller droplets, with the density of blood drops decreasing moving further away from the initial blood source. The study of impact spatter may provide insight into the relative position of individuals and objects during an incident and the nature of the incident.

34 Beating and Stabbing Spatter = larger individual stains. First blow usually doesn t result in spatter since there is not yet any exposed blood.

35 Gunshot Spatter = can result in a mistlike spatter that indicates a gunshot. If misting is present, it is most likely a gunshot. Not all gunshots will result in misting.

36 Gunshot Spatter Gunshots result in back spatter (where bullet enters) and forward spatter (where bullet exits).

37

38 Expiratory blood from the nose/mouth Often associated with injury to the respiratory tract, this type of bloodstain is caused by blood being coughed or otherwise expelled from the mouth. The stains will often be slightly diluted in appearance due to the additional presence of saliva or mucous. When blood is expirated from the mouth, it will often produce a pattern of small, round stains that could be likened to a fine mist.

39 Arterial spurt/gush This type of bloodstain results from the discharge of pressurized blood onto a target surface, for instance the ejection of blood from a punctured artery. Areas of the body in which wounding may cause arterial bloodstains include the carotid artery, the radial artery in the wrist, the femoral artery in the inner thigh, the brachial artery in the arm, temporal regions of the head, and the aorta. Blood is expelled from the artery as the heart continues to pump and, as the blood travels, it breaks up into smaller individual droplets.

40 Bloodstains produced will usually represent the beating of the heart as blood is expelled in periodic spurts. The resulting bloodstains can vary depending on a variety of factors, including: Whether the victim was stationary or moving as blood was being ejected, Where on the body the injury occurred and the extent of the wound. If a wound is smaller in size, naturally smaller blood drops will be produced, which can subsequently be expelled further from the injury site than larger blood drops

41 Blood pressure causes the blood to bleed out at a rapid, intermittent rate, in a spray or jet, coinciding with the beating of the heart. High amounts of blood and a wave pattern is observed on vertical surfaces.

42 Arterial Spray (Gushing)

43 Cast-off stains Cast-off bloodstains occur when centripital force causes blood drops to fall from a bloodied object in motion. If an object is repeatedly moved, each subsequent swing will result in less cast-off as less blood remains on the object. Bloodstains produced in this fashion can be particularly difficult to interpret as there is a great deal of possible variation in patterns produced. However depending on the nature of the motion of the bloodied object, cast-off blood will at least produce relatively linear stains.

44 Castoff Pattern can reconstruct where assailant and victim were positioned.

45

46 Cast Off

47 Expirated Bloodstain Pattern = Blood can accumulate in lungs, sinuses, and airway. Forcibly exhaled. Can appear like beating or gunshot pattern. May be mixed with saliva or nasal secretions.

48 Transfer Bloodstains These patterns are created when a wet, bloody object comes in contact with a target surface; may be used to identify an object or body part. Specific types of transfer patterns are: Contact: shoe print, weave pattern on pants. Wipe: a wipe through existing spatter. Swipe: finger smudge, wipe hand on clothing.

49 Contact Result when a bloodied surface or object comes into contact with another surface, transferring blood to create a pattern in the shape of an object.

50 Wipe A wipe pattern is created from an object moving through a preexisting bloodstain.

51 Swipe A swipe pattern is created from an object leaving a bloodstain.

52 Other Types of Patterns There are several other things that can be interpreted from specific things that happen to spatter.

53 Voids: Void patterns - indicating some object was removed or a person was hit by spatter.

54 Drying Time Drying begins at periphery and proceeds inward Drying time is affected by Surface type Amount of blood Climatic conditions Skeletonization Partially dry stains leave a ring that outlines original spatter. The drier the stain, the less skeletonization shown.

55 Clotting Time Clotting time outside the body ranges from 3 15 minutes. Spattered clots indicate that time passed between the initial bleeding and later blows. Coughing of clotted blood may indicate post-injury survival of victim.

56 Alteration of bloodstain over time Blood dries and clots over time. Difficult to estimate the time the blood exited the body. Clotted smears can indicate time of movement.

57 Always remember, before any calculations or measurements are taken, blood patterns must be documented!!

58