Bloodstain Pattern Analysis: Area of Convergence

Question 1

type of blood pattern on tip of one’s finger

Answer 1

passive/dropping

Question 2

diameter of drop of blood will ?

Answer 2

increase with distance

Question 3

what changes with the drop of blood as angle of impact increases?

Answer 3

shape

Question 4

angle of impact

Answer 4

angle at which the blood drop hits the target surface

Question 5

as angle decreases the drop becomes ?

Answer 5

more elongated

Question 6

tail of drop

Answer 6

points to the direction of travel

Question 7

what may determine direction of travel and relative traveling speed?

Answer 7

the more elongated the drop and the more distance between the drops = faster speed of traveling

Question 8

measurement of length and width of bloodstains for elongated and regular

Answer 8

elongated:
cut out tail
make a perfect oval (anything before tail)
length (top to bottom), width (across)
regular:
90 degree angles, cut out spines (rounded edges)

Question 9

equation for angle of bloodstain

Answer 9

angle = sin A (width/length) (in mm)

Question 10

what does sin A stand for?

Answer 10

width of bloodstain/length of bloodstain

Question 11

what does A stand for?

Answer 11

the angle of impact

Question 12

what is the error rate factor with the formula?

Answer 12

5 degree
the calculations are good to plus or minus 5 degrees of the actual value of the angle of impact
calculator Sin-1

Question 13

point of convergence

Answer 13

where did the impact occur; 2 dimensional
long axis or lengthof bloodstain

Question 14

how to find point of convergence

Answer 14

-by drawing a line through the long axis of a group of bloodstains is how the point of convergence can be determined
-lines of the group of stains intersect one another the convergence point can be established

Question 15

point of origin

Answer 15

where did the impact occur: 3 dimensional

Question 16

how to find point of origin

Answer 16

-use strings and mathematical equations to determine point of origin
-may have overlapping patterns or multiple patterns

Question 17

point of origin - string method

Answer 17

1. find the point of convergence for the stain pattern
2. place a yardstick as an axis coming from the point of convergence
3. attach one end of a string next to each droplet. place a protractor next to each droplet and lift the string until it lines up with the determined angle of impact of the drop. Keeping the string in line with the angle, attach the other end of the string to the axis (yard stick)
4. view the point of the origin of the drops where the strings appear to meet. secure the strings at this area