Presentation on theme: "Chapter Ten – Bloodstain Pattern Analysis FRSC 8104 Criminalistics II Professor Bensley."— Presentation transcript:
Chapter Ten – Bloodstain Pattern Analysis FRSC 8104 Criminalistics II Professor Bensley
FRSC 8104 – Bloodstain Pattern Objectives 1.Discuss the information that can be gained from bloodstain pattern analysis about the events involved in a crime. 2.Explain how surface texture, directionality, and angle of impact affect the shape of individual bloodstains. 3.Calculate the angle of impact of a bloodstain using its dimensions. 4.Describe the classifications of low-, medium-, and high-velocity impact spatter and appreciate how those classifications should be used. 5.Discuss the methods to determine the area of convergence and area of origin for impact spatter patterns. 6.Understand how various blood pattern types are created and which features of each pattern can be used to aid in reconstructing events at a crime scene. 7.Describe the methods for documenting bloodstain patterns at a crime scene.
FRSC 8104 – Blood Spatter Outline I.Introduction A.What is it? B.What can we learn from interpretations? II.Properties of Blood A.Basic Properties B.Shape of Drops 1.Surface Tension Way Cool Videos!
FRSC 8104 – Blood Spatter Outline C.Volume of blood drops D.Diameter of Stain vs. Distance Fallen 1.Maximum Terminal Velocity A high-speed photograph time series comparing the impact dynamics of three different droplet diameters. Impact velocity was 4.2 m/s and the surface was paper. http://www.hartnell.cc.ca.us/faculty/jhughey/Files/bloodstainshapes.pdf Videos 1 and 2
FRSC 8104 – Blood Spatter Outline III.Bloodstain Formation and Impact Angle A.Direction of Travel B.Angle of Impact Determinations 1.We love Trigonometry! Videos – 80 degrees (Top View) 80 degrees (Side View) 20 degrees (Top View) 20 degrees (Side View))
SIN < = Width (a) 1.5cm Length (c) 3.0cm Width (a) 1.5cm = SIN < Length (c) 3.0cm 0.5 = SIN < < = 30 degrees
FRSC 8104 – Blood Spatter Outline IV.Locating the Source of Bloodstains A.Point (AREA) of convergence http://www.fbi.gov/publications/leb/2005/feb2005/feb2005_img_31.jpg Video of Rat Trap at less than a 5 degree angle for Point of Convergence
FRSC 8104 – Blood Spatter Outline B.Point (AREA) of origin 1.Stringing Method 2.Trigonometry 3.Graph Paper 4.Computer (BPA Software) C.Limitations 1.Assume straight lines of travel 2.Surfaces other than horizontal
FRSC 8104 – Blood Spatter Outline V.Altering a Drop of Blood A.Changes in volume or changes in shape of resultant pattern B.What are goals of BPA? C.Various target surfaces 1.Texture 2.Thickness 3.Absorbency 4.Hardness
Blood Striking Various Surfaces Smooth, Non- Porous Surface (Glass) LinoleumCement Board Videos of Surfaces – Cotton, Wood, Cement
FRSC 8104 – Blood Spatter Outline D.Forces Acting upon Blood 1.Low velocity impact spatter a.Blood dripping into blood b.Splashed blood Gravitational pull up to 5 feet/sec. Relatively large stains 4mm in size and greater Videos: #1 #2
FRSC 8104 – Blood Spatter Outline 2.Medium velocity impact spatter a.Beating or stabbing Force of 5 to 25 feet/sec. Preponderant stain size 1 to 4mm in size Videos: #1 #2
FRSC 8104 – Blood Spatter Outline 3.High velocity impact spatter a.Gunshots, Explosions, Mechanical Accidents Force of 100 feet/sec. and greater Preponderant stain size 1mm in size and smaller Mist like appearance Videos: #1 #2
FRSC 8104 – Blood Spatter Outline 4.Projected Blood Pattern a.Running in, stamping in, or slapping a pool of blood b.Beating a head on the floor c.Arterial gushing or spurting
FRSC 8104 – Blood Spatter Outline 5.Cast Off Blood Patterns a.Blood being cast from a bloody object in motion onto a target surface b.Swinging a bloody hand or weapon c.Minimum number of blows delivered d.Technically not spatter Videos: #1 #2 #3