Bloodstain Pattern Analysis Flashcards

Presumptive testing for blood at a crime scene using luminol is most limited by which factor?

Answer: It can produce false positives with certain chemicals such as bleach or plant peroxidases

Luminol is a presumptive test that can produce false positives with oxidizing agents like bleach, copper compounds, and plant peroxidases, requiring confirmatory testing.

Which scenario would most likely produce a 'projected spatter' pattern rather than impact spatter?

Answer: Blood spurting from a severed artery under cardiac pressure

Projected spatter results from blood being propelled under internal pressure (e.g., arterial pressure from the heart), not from an external force striking a blood source.

A forensic consultant interpreting a bloodstain pattern should give most weight to:

Answer: The totality of physical evidence and scene context

Sound BPA interpretation requires integrating all physical evidence and scene context rather than conforming to a predetermined theory or relying solely on one category of evidence.

In a scene where blood is found on both the ceiling and floor, but not on nearby walls, the analyst should consider:

Answer: Arterial gushing directed upward followed by pooling

Blood on the ceiling and floor without wall staining could suggest upward arterial spurting that reached the ceiling, with gravity returning blood to the floor, though other hypotheses should be evaluated.

When calculating the angle of impact of a bloodstain, the analyst uses the formula arcsin(width/length). If the width is 8mm and the length is 16mm, the impact angle is approximately:

Answer: 30 degrees

Arcsin(8/16) = arcsin(0.5) = 30 degrees, meaning the droplet struck the surface at approximately 30 degrees from the surface plane.

Which characteristic of a bloodstain tail (satellite or wave cast-off) most reliably indicates the direction of travel of the blood droplet?

Answer: The tail or spines point in the direction of travel

The tail or spines of an elongated bloodstain point in the direction of the droplet's travel, allowing analysts to determine the direction from which blood came.

A CFC candidate reviewing a case notes that the defense claims blood was tracked into a room on a shoe after the incident. Which type of evidence would best support or refute this claim?

Answer: Shoe print transfer patterns with tread morphology and blood concentration gradients

Shoe print transfer patterns showing the tread pattern, decreasing blood concentration with successive steps (step-fade), and directionality can confirm or refute the tracked-blood hypothesis.