Major Blood Patterns
Bloodstains formed solely under the influence of gravity without any external force (e.g., drops, pools).
What are Passive Patterns?
A transferred subpattern that leaves drag marks and streaks across a surface by spreading blood around.
What is a Smear?
The three-letter framework forensic scientists use to build conclusions without relying on guesses or personal opinions.
What is C-E-R (Claim, Evidence, Reasoning)?
Directly seen or measurable facts gathered using your senses, such as "the man is crying" or "the man is dressed in all black."
What are Observations?
At a scene, an investigator notes: "The front door was wide open, and the suspect entered in a hurry." Which part of this sentence is an inference rather than a direct observation?
What is "the suspect entered in a hurry"?
The major pattern category created when a wet, bloodied surface comes into contact with a non-bloody surface.
What are Transfer (or Transferred) Patterns?
A transferred subpattern created when an existing bloodstain is touched and altered, but you can still see the original pattern underneath.
What is a Smudge?
In forensic analysis, these are direct, physical facts gathered from a crime scene, distinct from guesses or conclusions.
What are Observations (or Evidence)?
Conclusions or assumptions like "the man is going on a date" or "the date went badly," which are NOT direct observations.
What are Inferences (or Guesses/Assumptions)?
Investigators examining a damaged vehicle record that the car is a black Toyota with no broken windows, but has spray paint across the side doors. Which detail is irrelevant to determining whether targeted vandalism took place?
What is the car being a black Toyota (or having 4 doors)?
The major bloodstain category formed when liquid blood is propelled by an external force or energy through the air.
What are Projected Patterns?
A transferred subpattern formed when a bloody object is pressed down and lifted up, leaving an image shaped like the object.
What is a Print?
Before building a theory, forensic investigators must sort physical evidence into these two categories to focus on key clues.
What are Relevant and Irrelevant evidence?
The type of observation that directly helps investigators explain what happened or understand the main event at a crime scene.
What is a Relevant Observation?
In a case file, detectives find a suspect's DNA on a kitchen knife handle and the victim's DNA on the blade. Why is the DNA on the blade a crucial relevant observation compared to simply noting that a knife was in the apartment?
What is because it directly links that specific weapon to the victim?
A passive pattern resulting from blood dropping repeatedly into a line of motion while a person moves.
What is a Drip Trail (or Drip Pattern)?
A projected subpattern featuring lines of blood created by swinging a weapon back and forth multiple times.
What is Cast-off?
The part of the C-E-R framework where you explain the scientific logic that links your hard physical proof back to your claim.
What is Reasoning?
In "the car" do now scenario, this key observation provided the most relevant clue about what took place compared to details like door count or car make.
What is "cheater" spray painted on the passenger side doors?
While documenting a bathroom crime scene, an analyst records that a towel is on the floor, the tile is blue, and a bloody footprint sits on the bathmat. Which observation is irrelevant when reconstructing the suspect's path of movement?
What is the tile being blue?
A projected pattern characterized by fine, mist-like droplets created by a high-velocity force such as a gunshot.
What is High-Velocity Impact Spatter?
A projected subpattern formed when an artery is cut, spurting blood out in rhythm with the heart beat in oval shapes with heavy drips.
What is an Arterial Spurt?
A plausible conclusion or theory formed by combining and analyzing relevant observations from a case.
What is an Inference?
Observations such as "the car has 4 doors" or "the car is a Toyota" that do not help explain the specific event or crime.
What are Irrelevant Observations?
A report states: "A large, round pool of blood sat on the floor, showing that the victim bled out rapidly." What makes "showing that the victim bled out rapidly" an inference rather than a direct observation?
What is because it draws a conclusion about the speed/event rather than describing the physical stain itself?