CSI - Crime Scene Investigator Biological and Trace Evidence Questions and Answers

Question 1

An investigator uses a luminol-based test on a carpet at a homicide scene, which results in a positive reaction indicating the possible presence of blood.
Which of the following statements is most accurate regarding this result?

Accepted Answer

The test is a presumptive test and only suggests that blood might be present, requiring further confirmatory testing.

Answer

The luminol reaction is a confirmatory test, and no further analysis is needed to state that human blood is present.

Answer

A positive luminol result definitively proves the substance is human blood and can be used to identify a suspect.

Answer

The test is only considered valid if the resulting chemiluminescence is visible for more than five minutes without a light source.

Question 2

At a scene, a CSI finds several loose, dark fibers on a light-colored couch near the victim. Which of the following is the most appropriate method for collecting these fibers to prevent loss and contamination?

Accepted Answer

Using clean forceps to pick up individual fibers and placing them into a folded paper bindle, which is then placed in a labeled envelope.

Answer

Brushing the fibers directly into a large paper evidence bag.

Answer

Using a standard vacuum cleaner with a new bag to collect all debris from the couch.

Answer

Applying adhesive fingerprint tape to lift the fibers from the surface.

Question 3

A forensic lab receives a small, degraded bone fragment from a decades-old cold case. Investigators hope to link the remains to a maternal relative of the suspected victim. Which type of DNA analysis would be most suitable and likely to yield a result?

Accepted Answer

Mitochondrial DNA (mtDNA) analysis.

Answer

Short Tandem Repeat (STR) analysis of nuclear DNA.

Answer

Restriction Fragment Length Polymorphism (RFLP) analysis.

Answer

Y-STR analysis.

Question 4

An officer is collecting a Gunshot Residue (GSR) kit from the hands of a suspect who was apprehended three hours after a shooting. What is the correct procedure for using the SEM stubs for collection?

Accepted Answer

Use a dabbing or pressing motion to sample the web area between the thumb and index finger, as well as the palms.

Answer

Rub the stub vigorously across both the palm and back of each hand.

Answer

Use one stub for the right hand, one for the left hand, one for the face, and one as a control.

Answer

Moisten the stub with distilled water before applying it to the suspect's skin to improve adhesion.

Question 5

Which of the following pieces of trace evidence should be packaged in an airtight container to prevent its degradation or loss?

Accepted Answer

A piece of charred wood flooring suspected of containing an accelerant.

Answer

A single human hair with the root attached.

Answer

A blood-soaked piece of fabric that is still damp.

Answer

A small sample of dry soil from a shoeprint.

Question 6

A DNA profile is generated from a hair shaft (not the root). Which of the following is true about the evidentiary value of this profile?

Accepted Answer

It yields mitochondrial DNA (mtDNA), which can exclude individuals but cannot individualize; it can only associate a person with a maternal lineage.

Answer

It provides a unique nuclear DNA profile that can identify a single individual.

Answer

It cannot be used for any meaningful comparison as DNA is only found in the hair root.

Answer

It can be used to definitively link a suspect to a crime scene with the same certainty as a blood sample.