CSI Biological and Trace Evidence 2

Question 1

Which presumptive test for blood produces a blue-green color change in the presence of hemoglobin?

Accepted Answer

Leuco malachite green test

Answer

Leuco malachite green (LMG) produces a blue-green color when it reacts with the peroxidase activity of hemoglobin.

Question 2

What is the primary reason investigators use an alternate light source (ALS) when searching for biological fluids?

Accepted Answer

To cause biological fluids to fluoresce or absorb light differently

Answer

ALS causes many biological fluids like semen and saliva to fluoresce, making them visible in low-contrast environments.

Question 3

A fiber recovered from a victim's clothing is identified as nylon. Which microscopic characteristic best distinguishes nylon from polyester fibers?

Accepted Answer

Birefringence pattern under polarized light

Answer

Polarized light microscopy reveals distinct birefringence patterns that differ between nylon and polyester, aiding fiber discrimination.

Question 4

When collecting soil evidence, what is the recommended minimum number of reference samples that should be taken from around a scene?

Accepted Answer

At least four perimeter samples plus a control

Answer

At least four perimeter reference samples plus a control help establish the natural soil variation around the scene for comparison.

Question 5

Which enzyme is most commonly targeted in confirmatory tests for amylase to identify saliva?

Accepted Answer

Alpha-amylase

Answer

Alpha-amylase is produced in high concentrations in saliva and is the enzyme targeted in saliva identification assays.

(CSI) Crime Scene Investigator Practice Test