Evidence Collection & Forensic Analysis Flashcards

When a vessel's Voyage Data Recorder (VDR) is secured after a casualty, what is the first priority before downloading data?

Answer: Document the capsule's condition, seal number, and create a bit-for-bit forensic copy before analysis

Creating a verified forensic image preserves the original data integrity and allows the original capsule to remain untouched as the evidentiary master copy.

In a flooding casualty investigation, an investigator discovers a through-hull fitting with a cracked seacock body. What metallurgical analysis would best determine if the failure was pre-existing or sudden?

Answer: Scanning electron microscopy (SEM) to examine fracture surfaces for fatigue marks, stress corrosion, or overload failure patterns

SEM examination of fracture surfaces can distinguish fatigue cracks (beach marks, striations) from sudden overload failures, establishing whether the defect was progressive or acute.

A marine investigator needs to establish the exact time a vessel's engine room bilge alarm activated. Which source provides the most reliable timestamp for this determination?

Answer: The integrated alarm and monitoring system (AMS) electronic log with UTC-synchronized timestamps

An AMS electronic log provides automated, UTC-synchronized timestamps that are more reliable than human recollection or manually recorded entries.

During a collision investigation, both vessels' AIS tracks are examined. What limitation of AIS data must be considered when reconstructing the incident?

Answer: AIS position reports are transmitted at intervals, so the track interpolates movement between transmissions and may not reflect instantaneous maneuvers

AIS transmits at intervals based on speed and vessel type, meaning the reconstructed track interpolates position between actual transmissions and can miss rapid course or speed changes.

An investigator collects fabric samples from a suspected arson fire aboard a yacht. What is the proper method for preserving these samples for accelerant detection?

Answer: Seal samples in clean, unused paint cans or nylon bags to prevent accelerant evaporation

Airtight containers such as clean paint cans or nylon evidence bags prevent volatile accelerant compounds from evaporating before laboratory analysis.

What is the significance of finding high concentrations of carbon monoxide in a deceased crew member's carboxyhemoglobin level during a post-mortem examination?

Answer: It indicates the victim was alive and breathing in smoke-filled air, confirming they were alive during the fire

Elevated carboxyhemoglobin (COHb) levels confirm the victim inhaled combustion byproducts while alive, establishing they were present during the fire rather than already deceased.

A marine investigator interviews a crew member who witnessed a man-overboard event. Under what circumstance should the investigator stop the interview and reschedule?

Answer: When the witness appears acutely distressed, in shock, or physically impaired in a way that compromises their ability to provide reliable information

Interviews conducted when a witness is in acute psychological distress or physically compromised produce unreliable information and may constitute a coercive or unfair process.