Angular Impact Produced by Horizontal Motion

Answer

1. Angular Impact Produced by Horizontal Motion

   Introduction

   One of the major factors to be considered during Bloodstain Pattern Analysis (BPA) is angular impact produced by horizontal motion at the time the blood falls on the ground. When a free falling drop of blood is subjected to any force providing horizontal motion or faces a downward pull as a result of gravity, it is likely to have an angular impact on horizontal or vertical surfaces (Brodbeck, 2012). The angle of the impact is made by the width to length ratios on both surfaces. On the same note, the directionality is also created by the shape of the stain and the characteristics of the edges. Series of bloodstains which result from free falling drops that move in a particular direction with adequate horizontal motion may have scalloped edges on the foremost point which shows the direction from which the source of blood is going to or coming from (Brownson & Banks, 2010). Using the angular impact produced by horizontal motion, it is easy to determine whether the source of blood was from a fast or slow moving source. This may be used to establish if the person from whom blood came from was running or walking. The objective of this experiment, therefore, is to analyze the effect of the horizontal motion of blood applied to falling blood drops and correlate it to the resultant angular impact of bloodstain patterns and determine the direction of travel of the source of blood.

   Materials

   • A few drops of human blood
   • Glass pipette or dropper
   • Paper
   • Stopwatch
   • Tissue
   • Digital Camera
   • USB Microscope

   Procedure

   The paper was laid out on a table for a distance of six feet. A well-mixed human blood was drawn into the pipette and the excess blood on the outside of the tip of the pipette was wiped out. The initial drop onto tissue was squeezed to remove any air bubbles. The pipette was then held four inches above the target surface, and then there was a walk at a normal constant pace at a distant of six feet, allowing blood drops to fall on the target surface. With assistance, the number of seconds it took to travel the distance of six feet was measured and recorded using the stopwatch. The movement began several feet in front of the table and was terminated beyond the table to achieve the measurement of a uniform speed. The experiment was repeated with the person walking at a fast pace and at a running pace with the blood falling from the pipette four inches above the target surface. The experiment was again repeated with the paper on the floor and the pipette of blood held 36 inches above the target surface using a timed, normal, constant walk, fast walk, and a run.

   Results

   Target Surface: Table

    

   	Distance Fallen	Seconds	Velocity Ft/s	Amount Spatter	Width/ length Ratio	Angle of Impact
   Normal Walk
   	4	8	0.5	5	0.99	89.7
   	36	8	4.5	4	0.95	71.8
   Fast Walk
   	4	4	1	3	0.64	39.8
   	36	4	9	2	0.61	37.6
   Run
   	4	2	2	1	0.42	24.8
   	36	2	18	0	0.40	23.5

    

    

   Target surface: Floor

    

    

   	Distance Fallen	Seconds	Velocity Ft/s	Amount Spatter	Width/ length Ratio	Angle of Impact
   Normal Walk
   	4	8	0.5	5	0.95	71.7
   	36	8	4.5	4	0.93	68.4
   Fast Walk
   	4	4	1	3	0.61	37.5
   	36	4	9	2	0.59	34.6
   Run
   	4	2	2	1	0.39	24.8
   	36	2	18	0	0.37	23.5

    

   Discussion

   According to the results above, the angle of impact of blood drop can be determined. Notably, when blood falls straight down on the ground; that is, at an angle of 90 degrees, it forms a relatively circular spatter. This can only be found in cases where blood drop faces less horizontal forces during the time of drop Brownson & Banks, 2010).  As evidenced by the experiment, it was only found when the person was walking normally, and the blood fell from a distance of four inches. However, when the drop was suspended at 36 inches, it faced relatively heavy resistance hence there was further elongation. On the wave cast-off, blood that was moving (at an angle of commonness less than 90 degrees) had an elongated stain, and its tail pointed in the direction of movement of drop (Brownson & Banks, 2010). The blood also created a minor drop of blood that moved slightly in the direction of flow. This was demonstrated when the person was running and allowing blood to fall on the table. The angle of impact was about 24 and 22 on four and thirty-six suspension respectively.  Additionally, the blood drops had a tail which pointed back towards the larger "parent" drop. When blood fell onto on the table (smooth surface) the drop was able to spread out evenly without cossetting its surface tension hence the circular shape (Larkin & Banks, 2013). However, on the floor (the rough surface), the increasing edges of the drop are interrupted, making the blood to form an uneven shape.  It is also important to note that width/length ratio of blood drop is bigger on smooth surfaces than in rough ones because of it easy for blood to move long distance in smooth surface than rough surfaces hence longer lengths.