Presentation on theme: "Forensic Science Warning: Some material in this presentation and related videos may be too graphic for some people."— Presentation transcript:
Forensic Science Warning: Some material in this presentation and related videos may be too graphic for some people.
A bloodstain pattern is a physical, geometric image created by blood contacting a surface, or by a surface contacting blood. The geometric images of interest are primarily those created once blood leaves the body. What is a Bloodstain Pattern?
What does the abbreviation BPA represent? Bloodstain Pattern Analysis 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 How does a blood droplet form? Click the image for an animation.
Course surfaces cause irregularities in patterns. Blood may break up on impact, and may follow the contour of a surface (Bevel & Gardner, 2002). Impact angles and directionality become less reliable as a surface become more porous (inverse relationship). Impact Surface Considerations
Light Source Investigators will first examine the crime scene to look for areas that may contain blood. They may use a high-intensity light or UV lights to help them find traces of blood as well as other bodily fluids that are not visible under normal lighting conditions. How is blood evidence detected at a crime scene? 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 can determine if it is human blood or not. Examples: Phenolphthalein is a chemical that is still utilized today and is usually referred to as the Kastle-Meyer test and produces a pink color when it reacts with hemoglobin. 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. Kastle-Meyer Test Video HemaStix
Luminol This chemical is used by crime scene investigators to locate traces of blood, even if it has been cleaned or removed. Investigators spray a luminol solution is throughout the area under investigation and look for 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 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. Fluorescein This chemical is also capable of detecting latent or old blood, similar to luminol. It is ideal for fine stains or smears found throughout a crime scene. After the solution has been sprayed onto the substance or area suspected to contain blood, a UV light and goggles are used to detect any illuminated areas, which appear greenish-white if blood is present. It may also react to many of the same things as luminol (copper and bleach). Fluorescein Reaction in UV Light
Bloodstain Pattern Analysis Terms Spatter – Bloodstains created from the application of force to the area where the blood originated. Origin/Source – The place from where the blood spatter came from or originated. Angle of Impact – The angle at which a blood droplet strikes a surface. Parent Drop Spines Satellite Spatters 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.
Passive Bloodstains –Patterns created from the force of gravity –Drop, series of drops, flow patterns, blood pools, etc. Projected Bloodstains –Patterns that occur when a force is applied to the source of the blood –Includes low, medium, or high impact spatters, cast- off, arterial spurting, expiratory blood blown out of the nose, mouth, or wound. Transfer or Contact 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. –A wipe pattern is created from an object moving through a bloodstain, while a swipe pattern is created from an object leaving a bloodstain. Blood Spatter Movie Types of Bloodstain Patterns
Those patterns which generally result from the free flow of blood. Passive Flow Pattern – when blood flows freely. Passive Saturation Pattern – when blood flows to saturate an area. Passive Bloodstain Patterns
Passive Saturation – in cloth there may be secondary patterns from the cloth folded on itself. In some literature this is called a secondary transfer pattern. Passive Pool Pattern – when blood flows freely into a pool. Notice: trail, drip. trail drip Passive Bloodstain Patterns
Free flow around a surface notice pattern from lap and buttocks. Notice void areas in this passive pattern. Passive Bloodstain Patterns
Those patterns resulting from blood sent with a degree of energy, other than gravity, from an origin to a surface. Blood is shot, flung, or hurled at a surface, as examples. Arterial Spurt/Gush Pattern- blood which leaves the body under pressure: breached artery. *Note: rhythmic pattern. Arterial Spurt and Free Flow Projected Bloodstain Patterns
Expirated Pattern – blood projected from the mouth, nose, or a gaping wound. Often an expirated pattern is found with saturation and pool patterns. Notice the expirated pattern on the side of the chair, and the saturation pattern on the bed corner. The victim had a throat wound. Projected Bloodstain Patterns
Expirated patterns have the appearance of medium to low velocity blood spatter. Expirated patterns may also be found with arterial spurt patterns, and cast-off patterns. Expirated Pattern with Arterial Spurt. Projected Bloodstain Patterns
Instrumental Projected Patterns – These are patterns, that for lack of a better name, are caused, in part, by an instrument that is part of the origination of the blood spatter. Some examples of instruments are: knife, firearm, board, swinging hand, kicking foot, bat. The blood is projected from the instrument. High Energy - Shotgun Projected Bloodstain Patterns
Instrumental Projected Patterns: -High Energy (velocity): 100’/sec or more, firearms, airplane propeller, power equipment. -Often has a misting effect appearance, and spatters less than 1mm in diameter. -In the photos note the mass and misting areas. suicide test pattern Projected Bloodstain Patterns
Instrumental Projected Patterns: -Medium velocity: 25’/sec or more, swinging knife, bat, kicking foot, swinging hand, expirated, arterial. -No predominance of stains with a diameter less than 1mm. -A trail may present in a pattern from a swinging instrument (+1 rule). Medium energy(velocity) with transfer pattern. Projected Bloodstain Patterns
Instrumental Projected Patterns: –Low Velocity: free falling velocity, blood dropping from a cut finger, bleeding nose, other wounds, or a near immobile instrument. –Some literature designates as drop patterns. –Bleedings, walking subjects may leave a low velocity trail. drops at homicide dropped blood Projected Bloodstain Patterns
Size difference in free falling drips can be due to: distance, surface from which blood is dripping. Blood dripping into blood: notice the smaller “satellite” stains - compare these with the “radial” stains from a volume drop, or an object impacting a pool of blood. satellite Projected Bloodstain Patterns
Instrumental Projected Patterns: -Cast off: a special term reserved for spatters cast from an instrument. -cast off patterns seem to particularly apply to sharp force and blunt trauma instruments. -Wave cast off: term for a pattern resulting from a cast off from a cast off. *caution*. cast off from fleeing suspect Projected Bloodstain Patterns
Instrumental Projected Patterns: Cast off: A moving instrument may produce a pattern in which the blood spatter creates a “trail”. The “trail may reproduce several times. A very general rule is that the number of blows to a victim is one more than the number of “trails”. *caution*. Cast off “trail” on back side of pajama bottom –notice multiple “trail” or “arc” phenomena. Projected Bloodstain Patterns
Projected blood forming an arc that was from an assault with a hammer. Notice the mixture of patterns. arc Projected Bloodstain Patterns
Additional arc patterns, consistent with being struck with an object, are evident in the photo. Notice the mix with the contact pattern. The victim reported being repeatedly struck while covering up and trying to get away. Are the patterns consistent with the story? arccontact Projected Bloodstain Patterns
Instrumental Projected Patterns: Backspatter: generally applies to firearm phenomena in which the blood from the wound is also forced backwards onto the subject of a surface. -hands are common backspatter surfaces. -very easy to confuse with expirated blood. backspatter from gunshot wound. Projected Bloodstain Patterns
Impact patterns: produced when blood splashes. May be produced from blood falling into blood, or an object impacting blood. These patterns are called splash patterns in some literature. Characteristics: “spiny” edges, circumferential surrounding stains. Volume pattern: a volume of blood impacts surface, and falls into itself. Notice the radiating patterns. Impact Bloodstain Patterns
Impact Patterns: Drip: when blood drips into blood. Object splash: when an object impacts a volume of blood. *Caution: carefully try to establish any continuity.* Impact Bloodstain Patterns
Blood drips into blood and splashes onto the chair leg. An assault victim leaves a blood trail - notice the dripping, splashing, and adjacent bloodstains. Impact Bloodstain Patterns
Patterns created: surface contacts a surface leaving an impression. -transfer: bloody surface to secondary surface (bloody hand to wall).- contact: object surface contacts blood (shoe print)-swipe: bloody object moves across surface(hair). -wipe: object moves through blood (hand through drop). Transfer: notice outline of of parallel liner line pattern. This is a pattern from a arm touching the table. Impression Bloodstain Patterns
Notice the swipe patterns on the wall, and by the foot. Notice the wipe through the blood with the feathering of the stain, and the swipe to the left. Impression Bloodstain Patterns
Wipe: Notice the remaining skeleton of the original stain. The “feathering” out of the swipe indicates direction. Wipe: A little more difficult to tell. It almost looks like a swipe. This was made with a brush. Impression Bloodstain Patterns
A transfer pattern from the shotgun to the bed sheet. Knife blade and handle transfers. Impression Bloodstain Patterns
A contact pattern from a shoe at the scene of an assault. Knife transfer pattern from a homicide scene. Notice the handle pattern in the far left. Impression Bloodstain Patterns
A transfer swipe pattern from The scene of an assault. notice the mixture of the transfer, free flow, and cast off patterns. A very subtle swipe mark in carpet at the scene of a homicide. The marks start at upper center and arc downward. Impression Bloodstain Patterns
Impression patterns may be enhanced by the use of bloodstain dyes (Amido Black, Coomassie Blue), Luminol, Alternate Light Source, or Fluorescein. Since identity can often be established by DNA, a sample of any pattern should be taken prior to enhancement. Would Luminol have aided the carpet pattern in the previous slide? Luminol enhancement Impression Bloodstain Patterns
These are patterns that are extraneous to direct human blood loss. Fly artifacts: patterns created by flies. Bugs/insects: created by interaction with bugs. Blood: blood that dries, bubbles, or separates. Dried blood drop: skeletonized. Dried Blood: notice from outer edges in, & flaking away in right stain. Artifactual Bloodstain Patterns
Fly spots on the kitchen wall above the head of double homicide victims. Both victims received handgun head wounds. Fly spots on a window shade at a death scene. Notice the similarity to low-medium velocity. Artifactual Bloodstain Patterns
Air bubbles in blood on the blade of a knife. Fly spots on a window at a homicide scene. This is not a picture of a sperm cell. Artifactual Bloodstain Patterns
Blood has an adhesive quality. It may create a bonding phenomena between two surface. When separated one can observe the “alligatoring” effect. If a measurement is made after “bonding” it should be considered smaller than the actual object structure. Artifactual Bloodstain Patterns
It is not what it seems at first? This is a volume, free flow, drip and drop, and arterial spurt pattern. It is not a high velocity pattern. It was created, in part, by wind whipping around the edge of the building. Artifactual Bloodstain Patterns
**Impact angle calculations do not apply.** Directionality determinations are possible. Contact, transfer, & passive actions usually on one side. Projected related actions, volume actions usually on both sides. Always corroborate before making final inference. **The most difficult of all interpretations?** Blood on Clothing
Blood which impacts a surface at a 90 degree angle will be nearly round in shape. As the blood impacts at a angles decreasing from 90 degrees the pattern will become more elongated and elliptical. The angle of impact is that between the surface and angle line. Angle of Impact
- Direction of travel refers to the direction in which the blood spatter is moving from its origin to its destination. - It can be determined from spatters from the “tail”. -In free flow and swipes and wipes it can be determined by spatial relationships and feathering of the pattern. A line drawn through the center of the longest aspect (axis) of the stain, and in the direction of the “tail” points in the direction of travel. Direction of Travel of Bloodstain Patterns
Blood Spatter Labs You will be creating sample drop patterns using single drops and multiple drops. We will also investigate the effect of motion and the angle of impact on blood spatter. This can be messy! Be very careful to keep the blood on the paper and not on yourself, the table, or floor. Hold you hand as steady as possible when making the drops. Brace your wrist against the meter stick to help you. Get your materials from your teacher – paper, black marker, meter stick, goggles, and a bottle of blood. If you make a mess, clean it up immediately!
Lab 1: Single Droplets 2550 Single Drops Group Members Single Drops Group Members Label two large pieces of construction paper as shown below. To do the lab, put on your goggles and hold the dropper bottle upside down so that the end of it is 25 cm from the paper. GENTLY squeeze the bottle so that ONE drop of blood is released and lands in the correct location on your paper. It should NOT hit the meterstick. Repeat TWO more times at this height for a total of three drops. Continue making drops of blood on your paper, but put the drop in a different area of the paper and change the height each time. When you are done, analyze your results and answer the questions on your worksheet. Make a mistake? Use a paper towel to wipe it off your paper! Keep your drops in the correct area of the paper.
Use your results to answer these questions. What did you notice about the diameter of the parent droplets as you increased the height of the drop? How do the spines compare from the different heights? Lab 1 Questions
Lab 2: Multiple Droplets Label a long piece of butcher paper (2 -3 meters in length) as shown below. To do the lab, put on your goggles and hold the dropper bottle upside down so that the end of it is 25 cm from the paper. GENTLY squeeze the bottle so that ONE drop of blood is released and lands in the correct location on your paper. The drop should NOT hit the meterstick. Without moving your hand, release ONE more drop onto the first drop at that height. If you make a mistake, wipe it off with a paper towel and try it again. Continue making drops of blood on your paper so you have three sets for each height. When you are done, analyze your results and answer the questions on your worksheet. Clean up your area and put away your materials before you leave class. Multiple Drops Group Members Keep your drops in the correct area of the paper.
Use your results to answer these questions. What happened when one drop landed on top of another one? What did you notice about the diameter of the parent droplets as you increased the height of the drop? What do you notice about the diameter of the satellite spatter as you increased the height of the drop? Lab 2 Questions
Lab 3: Motion Droplets During this lab, you will see how motion affects the size and shape of the droplets and spines. You will need a long piece of butcher paper (4-5 meters in length) and tape to secure it to the floor. You will also need safety goggles. To do the lab, you will need to hold the dropper bottle upside down so that your hand is out and away from your body (waist level), but is still over the paper. Start off walking at a SLOW WALKING RATE along the paper strip from one end to the other and GENTLY squeeze the bottle as you walk so that blood is released ONE DROP at a time. Be sure that all the drops land on your paper strip. Repeat this procedure using a NORMAL WALKING RATE and a FAST WALKING RATE. Walking Direction When you are done, analyze your results and answer the questions on your worksheet. Clean up your area and put away your materials before you leave class. Miss the paper? Use a paper towel to wipe it off the floor!
Use your results to answer these questions. Draw a sketch of the droplets showing the size, shape, and/or distance between them at each speed in the chart below. What did you notice about the shape of the droplets as you increased your walking speed? What did you notice about the spines as you increased your walking speed? What did you notice about the distance between the droplets as you increased your walking speed? Lab 3 Questions
You will be creating sample drop patterns created by droplets landing at different angles from the same height. Label five pieces of copy paper with your names and then indicate the angle for each droplet - 15 o, 30 o, 45 o, 60 o, or 75 o. Place the first piece of paper on the clip board and align the clipboard with the 15 o line. Hold the bottle of blood at a height of 50 centimeters from the top of the table. GENTLY squeeze the bottle so that ONE drop of blood is released and lands on the paper. Repeat two more times at this angle. Continue testing by dropping blood from a height of 50 centimeters at each of the other angles. Lab 4: Angle of Impact When you are done, answer the questions on your worksheet. Clean up your area and put away your materials before you leave class. Angle Guide Clipboard & Paper Height of 50 cm
Use your results to answer the question. What did you notice about the shape of the droplets as you increased the angle of the paper? Lab 4 Questions
Which of the three blood droplets shown would have been created by a wound in the lower part of the leg? Explain. If you find a trail of blood with droplets that are round and close together, what could this mean? If you have a blood droplet as shown at left, what does it tell you? Explain.