Bloodstain Pattern Analysis

Question 1

Who is SWGSTAIN and what do they do?

Answer 1

Scientific working group on bloodstain pattern analysis (BPA) - developed list of terminology and such that analysts use

Question 2

What are the three categories of bloodstains?

Answer 2

Passive, transfer and impact stains

Question 3

Passive stains, define:

Drip pattern

Drip stain

Drip trail

Answer 3

Drip pattern: from liquid dripped into other liquid

Drip stain: stain from falling drop hitting a surface

Drip trail: source of drip stains moved (think bleeding person or blood dripping off a weapon)

Question 4

Passive stains, define:

Expiration + Aspiration patterns
Flow pattern
Projected pattern

Answer 4

Expiration: blood forced by air out of nose/mouth/wound
Aspiration: air bubbles seen in blood
Flow pattern: blood moving on surface due to gravity (like running down a wall)
Projected pattern: ejection of blood under pressure (like an artery blew)

Question 5

Passive terminology, define

Satellite stain
Serum stain
Cast-off pattern

Answer 5

Satellite: smaller stains from blood that bounced off of a parent stain
Serum stain: typically yellow, from stuff that separated from red blood cells
Cast-off: from a moving object, typically arch shaped.

Question 6

Passive terminology (last one thank god)

Insect stain
Swipe pattern
Wipe pattern

(DO NOT CONFUSE SWIPE AND WIPE THEY ARE DIFFERENT)

Answer 6

Insect stain: from insect activity (ie insect with blood on it moved elsewhere?)
Swipe: blood from one surface wiped onto another surface
Wipe: blood ALREADY ON a surface wiped across THAT SAME SURFACE

Question 7

Impact terminology

Backspatter
Forward spatter
Mist

Answer 7

Backspatter: blood travelling opposite direction of force
Forward spatter: blood travelled same direction as force
Mist: blood microdroplets (like blood in a sneeze probably)

Question 8

Miscellaneous terms:

Blood clot
Bubble ring
Directionality
Edge characteristic

Answer 8

Clot: from red cells/platelets/fibrinogen/etc
Bubble ring: bubble/circle shaped stain
Directionality: features showing which way blood was travelling
Edge characteristic: features of the periphery of a stain

Question 9

Misc. terms

Perimeter stain
Void

Answer 9

Perimeter stain: altered stain but remaining peripheral characteristics
Void: gap in a pattern (probably an object in the way)

Question 10

What does blood do?

Answer 10

Delivers nutrients and O2 and removes waste from cells

Question 11

What are the ingredients of blood?

Answer 11

Red blood cells (erythrocytes, have hemoglobin which looks red)
White blood cells (leukocytes, immune function)
Platelets

Question 12

6 features for analyzing bloodstains

Answer 12

1. Direction of origin
2. Angle blood hit
3. Location when wound happened
4. Movement of bleeding person
5. Minimum # of blows struck
6. Rough location of assailant

Question 13

What is the equation to determine the angle of impact?

Answer 13

sinA = (width of stain/length of stain)

A = angle of impact

Question 14

How does the angle of impact determine the look of a bloodstain?

Answer 14

Steeper angle = more elongated w a tail

Lesser angle = more circular

Question 15

Define area of convergence + area of origin

Answer 15

Area of convergence: the spot in 2D where stains can be traced back to

Area of origin: the 3D space where the event happened (found with photographs and software, formerly string and a pole)

Question 16

Methods to document:

Grid method
Perimeter ruler method

Answer 16

Grid: making a grid over the pattern to keep track of which stains samples are from

Ruler: measuring shit with rulers lol