Forensics Crime Scene Practice Test 2026 - Free Crime Scene Investigation Practice Questions and Study Guide

The key idea is to preserve the sample's chemical profile and prevent contamination so that any accelerant residues can be accurately detected by instrumental analysis. Collect charred debris with clean, dedicated tools and immediately place it into airtight, chemically inert containers (such as glass vials with tight seals) to keep volatile components from escaping and to avoid introducing new contaminants. Proper sealing, labeling, and a clear chain of custody are essential to maintain sample integrity from the scene to the lab.

For analysis, GC-MS or headspace GC-MS are standard because they separate and identify volatile and semi-volatile hydrocarbons that can indicate accelerants even within burnt debris. Headspace sampling is particularly helpful for capturing vapors that may evolve from the debris, increasing the chance of detecting trace residues.

Including controls—such as field blanks and lab blanks—helps distinguish true accelerant signals in the debris from background environmental contamination or lab-derived artifacts. This strengthens the reliability of any identifications.

Rinsing with water, storing debris in a plastic bag without containment, or restricting collection only to scenes where accelerants are suspected all risk altering or missing residues, leading to false negatives or contamination. The described approach ensures evidence integrity and reliable analytical results.