Type-Oh!
What type of blood cell carries the proteins that determine blood type?
Red Blood Cells!
A bloody handprint on the wall. What type of bloodstain pattern is this?
Transfer Pattern
Is a cast-off blood pattern an example of high-, medium-, or low-velocity blood spatter?
Cast off is medium velocity
What is the purpose of a Presumptive Test?
To determine if a stain is blood or not blood. (could be animal blood!)
Using the bloodstain patterns on the walls, how could you determine the approximate location where the victim was standing when an attack happened?
The victim was likely standing near the area where the projected paths of blood droplets intersect, known as the area of convergence.
Name the three proteins that may be found in a blood sample that determine blood type.
A protein, B protein, D (Rh) protein
Something smeared through blood on the floor. What type of bloodstain pattern is this?
Wipe Pattern
Describe Low Velocity blood patterns, how are they formed?
Drops or pools of blood, formed when blood falls due to gravity (no force applied) also known as Passive blood stains
What is the purpose of chemical treatments such as Luminol, Fluorescein, and Leuco Crystal Black?
These chemicals are applied to find latent blood stains (stains that cannot be seen with the eye)
As the angle of impact for a blood drop becomes smaller, the shape of the drop…
As the angle decreases the drop becomes more elongated
Name the blood type proteins found in a person’s blood who is O-.
O- blood type has none of the blood type proteins!
What is cast off, how is it produced?
When a person is attacked with a weapon, blood will cover the weapon and fling off of it, creating a trail of blood for each swing.
Describe the appearance of High Velocity spatter. What usually causes it?
Blood drops are very small, a mist of blood, usually caused by gunshot
What are ‘spines’ on a blood drop? What condition would cause drops to form many spines?
Spines radiate out from a blood drop, when it falls - more spines if it falls from a greater distance, more spines when it falls on a hard surface.
You have measured the angle of five different drops in the corner walls of a room. Describe how to use this information to determine where the victim was standing.
Extend lines out from each drop (using lasers or string) at the calculated angle. The lines will cross at the approximate location of the victim when attacked.
Blood type is ________ Evidence!
Class
Name two things we can learn from studying cast off patterns at a crime scene.
The approximate number of blows a victim received, approximate location in the room during the attack, approximate size of the weapon used
Describe Medium Velocity spatter patterns. How are they formed?
Medium Velocity patterns are drops that are flung with force against a surface (wall, floor, ceiling, etc). Drops may come directly from a victim during an attack (drops fan out from central location), or fling off of the weapon (trail/line of blood drops).
What are ‘satellites’ in a spatter pattern? What condition would cause drops to form many satellites?
Satellites are tiny drops of blood that spring out of the main drop due to force of impact. Dropping from greater distance, and especially dropping into a pool of blood.
How do you determine the direction in which blood droplets are traveling?
the 90 degree drop hit the wall from straight on, perpendicular to the wall. Other droplets will have spines that travel in the direction it is moving.
You want to know if B protein is present in a blood sample. Describe how you would find out.
Add anti-B serum to the sample. If the blood clumps, the protein is present.
What blood stain pattern are the drops of blood?
Low velocity (passive)
What else causes high velocity spatter? How can you tell the difference?
Expository blood out of mouth or nose, will have salivary secretions mixed into the blood
What blood type is most common?
O+
If the blood clumps with anti-B, does this mean the blood type is B? Explain.
It means there is B protein present in the blood - but there also could be A, and/or Rh. So the blood type could be B-, B+, AB- or AB+