Evidence Collection and Preservation Flashcards

An investigator arrives at a scene where the decedent has a suspected contact gunshot wound to the head. To best preserve potential gunshot residue (GSR) on the decedent's hands for analysis, what is the most appropriate initial action?

Answer: Carefully place clean, unused paper bags over the hands and secure them with tape.

Placing paper bags over the hands is the crucial first step to prevent the loss or contamination of fragile gunshot residue evidence during movement and transport of the body. While photography, DNA collection, and fingerprinting are important parts of the investigation, they should be done after the hands have been protected, or in a controlled environment, to avoid dislodging the microscopic GSR particles.

What is the primary legal purpose of maintaining a strict chain of custody for all evidence collected at a death scene?

Answer: To document the chronological history of the handling, transfer, and storage of evidence to ensure its integrity and admissibility in court.

The chain of custody is a formal, chronological record documenting the continuous possession of an evidence item from its point of collection to its presentation in court. Its primary purpose is to prove that the evidence has not been altered, substituted, or tampered with, thereby ensuring its authenticity and legal integrity for admission in a court of law.

Which of the following is the LEAST appropriate container for packaging wet, blood-stained clothing collected from a death scene for long-term storage?

Answer: A sealed plastic bag.

Sealing wet biological evidence, like blood-stained clothing, in an airtight plastic bag is inappropriate because it traps moisture. This promotes the growth of bacteria and mold, which can rapidly degrade DNA and other biological material, potentially destroying the evidentiary value. Evidence of this nature should be air-dried in a controlled environment and then packaged in breathable paper containers.

At the scene of a suspected prescription drug overdose, an investigator finds multiple prescription bottles belonging to the decedent. What is the most critical information to document about the medications at the scene?

Answer: The name of the prescribing physician, the drug name, the fill date, and the number of pills remaining versus the number dispensed.

While all details can be useful, documenting the prescribing physician, drug name, fill date, and performing a pill count is most critical. This information helps establish a timeline, identifies potential "doctor shopping," and allows investigators to determine if the quantity of medication taken is consistent with the fatal overdose, which is crucial for determining the cause and manner of death.

The concept that every contact leaves a trace, which is the fundamental principle behind the collection of hair, fiber, and soil evidence, is known as:

Answer: Locard's Exchange Principle

Locard's Exchange Principle is a foundational concept in forensic science which states that whenever two objects come into contact, there is a transfer of material between them. This principle is the basis for collecting trace evidence such as hairs, fibers, paint chips, and soil, as their presence can link a suspect to a victim or a scene.

An investigator is collecting a single, small, dry bloodstain from a tile floor. Which of the following is the most appropriate method for collection?

Answer: Slightly moistening a sterile cotton swab with distilled water, swabbing the stain, and allowing the swab to air-dry before packaging.

The correct procedure for collecting a dry stain is to use a sterile swab slightly moistened with sterile or distilled water to concentrate the sample. The swab must then be thoroughly air-dried before being placed in a paper or swab-box container to prevent degradation. Scraping can cause the sample to flake and be lost, and using a wet towel would dilute the sample excessively.