ETC ETC Biological & DNA Evidence 2 — Questions and Answers
Question 1: What is the purpose of the Combined DNA Index System (CODIS)?
- A national database that stores DNA profiles to link crime scene evidence to known offenders or unsolved cases (Correct answer)
- A laboratory instrument used to sequence DNA samples
- A federal standard for packaging biological evidence
- A court database that stores trial evidence for appeals
Correct answer: A national database that stores DNA profiles to link crime scene evidence to known offenders or unsolved cases
CODIS is the FBI-managed national DNA database that contains profiles from convicted offenders, arrestees, and forensic unknowns, enabling matches between crime scenes and known individuals.
Question 2: When collecting a buccal swab (DNA reference sample) from a suspect, which area of the mouth is swabbed?
- The inner cheek (buccal mucosa) using a firm rotational swabbing motion (Correct answer)
- The gums adjacent to the front teeth only
- The tongue surface for maximum cell yield
- The roof of the mouth (palate)
Correct answer: The inner cheek (buccal mucosa) using a firm rotational swabbing motion
Buccal swabs collect epithelial cells from the inner cheek (buccal mucosa), providing a clean reference DNA sample; multiple swabs from both cheeks may be collected.
Question 3: Bloodstain pattern analysis (BPA) can help investigators determine which of the following?
- The direction, speed, and origin of blood shed at the crime scene (Correct answer)
- The blood type and DNA profile of the victim
- The approximate time of death based on drying patterns
- The victim's medical history from antibody markers in blood
Correct answer: The direction, speed, and origin of blood shed at the crime scene
BPA examines the size, shape, distribution, and directionality of bloodstains to reconstruct the events that produced them, including point of origin and movement.
Question 4: What type of bloodstain results from blood dripping into existing blood at a lower velocity?
- Satellite spatter pattern with secondary droplets around the primary stain (Correct answer)
- Cast-off pattern in an arc
- Impact spatter from a blow
- Transfer pattern from contact with a wet blood source
Correct answer: Satellite spatter pattern with secondary droplets around the primary stain
When blood drips into pooled blood, secondary satellite droplets are produced around the primary stain, indicating blood dripping at low velocity onto a wet surface.
Question 5: Which biological sample from a suspect provides the longest window for detecting alcohol consumption?
- Hair (EtG in hair — up to 90 days) (Correct answer)
- Blood (up to 12 hours)
- Urine (up to 80 hours)
- Saliva (up to 24 hours)
Correct answer: Hair (EtG in hair — up to 90 days)
Ethyl glucuronide (EtG) incorporated into hair can detect alcohol consumption for up to 90 days, far exceeding blood, urine, or saliva windows.
Question 6: What is luminescence testing used for in biological evidence processing?
- To detect latent bloodstains or other biological fluids that are not visible to the naked eye (Correct answer)
- To permanently label evidence packaging with UV ink
- To sterilize biological samples before laboratory analysis
- To photograph fluorescent trace evidence under white light
Correct answer: To detect latent bloodstains or other biological fluids that are not visible to the naked eye
Alternate light sources and luminescent reagents like luminol reveal blood and other biological fluids that have been cleaned or diluted, making invisible stains visible for collection.
ETC ETC Biological & DNA Evidence 2
What is the purpose of the Combined DNA Index System (CODIS)?