The Forensics of Blood: Checkpoint 1

Front

Which forensic question is addressed first when investigators find a blood-like substance at a crime scene?

Back

Is this substance blood?

Front

In the luminol test, which component in blood reacts with luminol that leads to chemiluminescence?

Back

Hemoglobin

Front

Which statement best describes the Kastle–Meyer test in forensic analysis?

Back

A presumptive test in which hemoglobin reacts with phenolphthalein causing a pink color change

Front

Why is the Kastle–Meyer test considered presumptive rather than confirmatory?

Back

Other substances besides blood can catalyze the color change

Front

What is the main purpose of the precipitin test in forensic biology?

Back

To determine whether blood is of human or nonhuman origin

Front

In a precipitin test, the bloodstain forms a precipitate when mixed with anti‑human antibodies from another animal species. What does this result most directly indicate?

Back

The stain is of human origin

Front

Which statement correctly distinguishes antigens and antibodies in the ABO system?

Back

Antigens are proteins on red blood cell surfaces; antibodies are proteins in blood plasma that bind foreign antigens

Front

Which antigens and antibodies are present in blood type A?

Back

Antigen A on red cells; anti-B in plasma

Front

A patient’s blood agglutinates with anti-B antibodies but not with anti-A antibodies. What is the patient’s blood type?

Back

Type B

Front

Crime scene investigators add an unknown blood sample to anti-A antibodies. The cells clump. What does this indicate about the cells?

Back

They carry A antigens on their surface