FDC Evidence Collection & Preservation 4

Question 1

When collecting fingernail scrapings from a deceased victim for touch DNA analysis, the collector should use a:

Accepted Answer

Clean wooden or plastic stick to scrape under each nail separately, changing tools between fingers

Answer

Each finger must be scraped with a separate tool to prevent cross-contamination between fingers, and non-metallic tools are preferred to avoid static that disperses trace material.

Question 2

Which condition MOST accelerates hydrolytic degradation of DNA in a biological sample stored at room temperature?

Accepted Answer

High relative humidity above 60%

Answer

High moisture content promotes hydrolysis of phosphodiester bonds and accelerates microbial growth, both of which fragment DNA rapidly at room temperature.

Question 3

In a sexual assault case where the victim has bathed prior to examination, which body location MOST likely retains spermatozoa suitable for DNA analysis?

Accepted Answer

Cervical os and cervical canal

Answer

Spermatozoa can persist in the cervical canal for up to 5–7 days because the cervical mucus protects them from the mechanical removal of bathing.

Question 4

According to FBI Quality Assurance Standards, a forensic DNA laboratory must conduct reagent blank testing to:

Accepted Answer

Detect DNA contamination introduced by laboratory reagents or consumables

Answer

Reagent blanks (extraction and amplification blanks) detect any exogenous DNA introduced via laboratory reagents, plasticware, or environmental contamination during processing.

Question 5

When packaging multiple items from the same crime scene into a single evidence bag for submission, the PRIMARY risk is:

Accepted Answer

Increased risk of cross-contamination between items

Answer

Packaging multiple items together risks DNA cross-transfer between items during transport, potentially creating mixed profiles that obscure the true source of evidence.

(FDC) Forensic DNA Certification Practice Test

(FDC) Forensic DNA Certification Practice Test

FDC Evidence Collection & Preservation 4