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Blood Spatter Analysis: Betrayal in a Suicide Attempt

Explore blood spatter patterns and eccentricity in forensic investigations. Learn to determine impact angles and direction of blood drops, uncovering hidden secrets in crime scenes. Understand the science behind blood spatter alteration and how it helps in investigations.

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Blood Spatter Analysis: Betrayal in a Suicide Attempt

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  1. Blood Spatter Lab Blood spatter from a sneeze from a bloody nose

  2. A couple decided to commit suicide after going through a hard time so they decided to jump off of a building together. When they got to the top they both counted to 3. The woman jumped but the man stayed behind. He watched the woman fall for 8 seconds, then saw her pull a string to a parachute she had hidden under her clothing. Who betrayed who?

  3. “Remember… it’s blood ‘Spatter’ not blood SpLatter.”

  4. Blood Drop blood spatter animations

  5. Eccentricity: of an ellipse is the ratio of the distance between the foci to the length of the major axis; this is necessarily between 0 and 1. If the ellipse has the Cartesian equation

  6. Basically “eccentricity” is how “oval” and ellipse is…. Which one is most “eccentric?”

  7. Measuring the shape of the blood drops

  8. Impact angle = sin-1(arcsin) width (d) length (D)

  9. drop on left: W = 1.8 cm L = 2.8 cm Impact angle = sin-1 (arcsin) width length = sin-1 (arcsin) 1.8 cm 2.8 cm = sin-1 (arcsin) (0.643) = 40 degrees

  10. drop on right: W = 1.2 cm L = 5.23 cm Impact angle = sin-1 (arcsin) width length = sin-1 (arcsin) 1.2 cm 5.23 cm = sin-1 (arcsin) (0.229) = 13 degrees

  11. Formula for Table 1 Angle of Impact Impact angle = sin-1(arcsin) width length ¼” = one foot on diagram on your answer sheet Formula for Table 2 Height above point of target XY = tan(i) x XJ, angle i being the angle of impact from the previous data table

  12. Blood Spatter 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

  13. Blood Spatter Determining Direction of Blood • The angle can be determined mathematically. • Width/Length, then take the inverse sin (sin-1). • This number is the impact angle (90 = perpendicular to surface; <10 at a sharp angle)

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