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DNA Quiz 2
| Question | Answer |
|---|---|
| What Is Bloodstain Pattern Analysis? | Scientific study of the static consequences resulting from dynamic blood shedding events |
| analyzing bloodstains | involves detecting, describing, and analyzing the size, shape, location, distribution, number, and pattern of bloodstains, as well as the nature of their target surfaces and relationship among various bloodstains at the scene |
| BPA is part of a multi-discipline investigation: | Physical evidence (Fingerprints, footwear impressions). DNA analysis. Witness statements. Forensic pathology. Electronic evidence |
| BPA is an applied science, based upon several other scientific disciplines: | Biochemistry Physics Fluid mechanics (dynamics) Trajectory analysis (ballistics) Chemistry |
| Bloodstain patterns are | predictable and reproducible. |
| Liquid blood will behave | according to the laws of physics |
| The appearance of a bloodstain | is surface dependent |
| The direction a bloodstain was moving can usually | be determined by its appearance (shape) |
| What Information Can BPA Provide? | Location of the blood source at the time of impact. • The minimum number of impacts to the blood source. • The mechanism or object used to create a specific pattern. • Position of a person/object during and/or after bloodletting |
| What Information Can BPA Provide? | Movement and directionality of a person who is bleeding or an object that is shedding blood. • Sequence of events |
| Origins of Bloodstain Pattern Analysis | Dr. Eduard Piotrowski (1895) University of Krakow, Poland Authored – Origin, Shape, Direction, and Distribution of Bloodstains Following Head Wounds Caused by Blows. |
| Origins of Bloodstain Pattern Analysis | Recognized the dynamic nature of blood in flight as a result of blows (impacts). Conducted experiments striking live rabbits with various implements. • Documented the resulting bloodstain patterns through hand drawings. |
| Bloodstain Pattern Analysis in Canada | Canada 1872 – The Queen vs. Campbell (Murder). Dr. Moore sr. (Western University) and Dr. Foster described bloodstains found on the suspects dress, found at the scene. |
| Bloodstain Pattern Analysis in Canada | Canada 1878 – R vs. McPherson & Burke (Rape/Murder). Professor Ellis (U of T) described bloodstains found on the suspects clothing. Stated that the suspects trousers had been washed after being bloodstained, based on chemical tests for blood |
| Bloodstain Pattern Analysis in Canada | Dr. Fred Carter (PhD, Physics) in 1989 developed software for blood drop simulation and area of origin calculations (BackTracks) |
| Blood Properties | • Approximately 5 litres in average adult. • 55% plasma (serum). • 45% formed elements (red & white blood cells, platelets). • Non-Newtonian fluid (shear thinning). |
| Viscosity: | Resistance to movement or flow. Blood is approximately 3-5 times more viscous than water. Resistance of fluid to flow or deformation |
| Surface Tension: | Elastic-like property of the surface of blood that tends to make it contract. Caused by cohesive forces of molecules within blood. |
| blood viscosity decreases | as shear force is applied. This allows blood to move through small blood vessels |
| Blood is a | non-Newtonian fluid or shear thinning fluid |
| Other shear-thinning fluid examples: | • Ketchup. • Whipping cream. • Motor oil. |
| Shear-thickening fluid examples: | • Corn-starch and water (“Oobleck”). • Silly Putty. • Honey. |
| The ability of blood to reproduce specific patterns is not affected to any significant degree by: | • Age • Sex • Alcohol / drugs • Disease process |
| Blood produces patterns that are: | • Predictable • Reproducible • Established through research, crime scene experience and experimentation |
| Directionality of Bloodstain | The term used to describe the direction of a blood droplet was travelling when it impacted the target surface. Directionality may be determined by the geometric shape of the bloodstain |
| Bloodstains/patterns created or formed by the force of gravity acting alone | Drip Stain • Drip Trail • Drip Pattern • Splash Pattern • Pool • Saturation Stain • Flow |
| Drip stains are | created when blood falls onto a surface due to the force of gravity. The formation and appearance of bloodstain patterns is surface dependent |
| Drip Trail | A bloodstain pattern resulting from the movement of a source of drip stains between two points. |
| Drip Trail | A drip pattern is created when a liquid drips into another liquid, where at least one of the two is blood |
| Splash Pattern | A bloodstain pattern created from a volume of liquid blood falling onto a surface |
| Pool Pattern . | A bloodstain resulting from an accumulation of liquid blood on a surface |
| Flow Pattern | A bloodstain resulting from the movement of a volume of blood on a surface due to gravity or movement of the target. |
| Saturation Stain | A bloodstain resulting from the accumulation of liquid blood in an absorbent material |
| Transfer Bloodstain Patterns | A bloodstain resulting from contact between a blood-bearing surface and another surface |
| Swipe Patterns | A swipe is a bloodstain resulting from the transfer of blood from a blood-bearing surface onto another surface, with characteristics that indicate relative motion between the two surfaces. |
| Wipe Patterns | A wipe is an altered stain resulting from an object moving through a preexisting wet bloodstain |
| Spatter Bloodstain Patterns | A bloodstain resulting from an airborne blood drop created when external force is applied to liquid blood |
| Spatter Bloodstain Patterns | Projected Pattern • Cast-off Pattern • Cessation Pattern • Expiration Pattern • Impact Pattern • Firearms Related Spatter |
| Projected Pattern | A bloodstain pattern resulting from the ejection of blood under hydraulic pressure, typically from a breach in the circulatory system |
| Cast-Off Pattern | A bloodstain pattern resulting from blood drops released from an object due to its motion. |
| Cessation Pattern | A bloodstain pattern resulting from blood drops released from an object due to its abrupt deceleration. |
| Expiration Pattern | A bloodstain pattern resulting from blood forced by airflow out of the nose, mouth, or a wound |
| Impact Pattern | A bloodstain pattern resulting from an object striking liquid blood |
| Impact Pattern – Area of Origin Estimation | The space in three dimensions to which the trajectories of spatter can be utilized to determine the location of the spatter producing event. |
| Impact Pattern – Angle of Impact | The acute angle between the path of travel of a blood droplet and the surface it strikes. |
| Impact Pattern – Area of Convergence | The space in two dimensions to which the directionalities of spatter stains can be retraced to determine the location of the spatter producing event |
| Classification Exceptions – Altered Stain | A bloodstain with characteristics that indicate a physical change has occurred, Drying, Clotting, Serum Separation, Decomposition, dilution (clean up), insect activity |
| Classification Exceptions – Voids | An absence of blood in an otherwise continuous bloodstain or bloodstain pattern |
| chemical enhancements | amido black, hungarian red, leuco crystal violet LCV, luminol, bluestar |
Created by:
skyep25