Understanding the layers of drug evidence is critical to any criminal defense strategy that involve drugs. In Missouri, cases typically move through a forensic hierarchy—starting with subjective roadside tests and culminating in precise laboratory analysis. While law enforcement often relies on rapid field results to make arrests, these “presumptive” tests are not always conclusive and can be challenged in court.

The Forensic Evidence Hierarchy

The strength of a drug case depends on the reliability of the testing method used. In Missouri, this generally follows a three-stage process:

1. Chemical Reagent Field Tests: These are color-based tests (like NARTEC and and MobileDetect) used at the scene. They are inexpensive but known for “false positive” results because the chemicals can react to legal household substances.
2. Handheld Laser Analyzers: Devices like TruNarc use more advanced technology, such as Raman spectroscopy or automated algorithms, to identify over 500 substances in seconds. While more sophisticated, they are still considered preliminary and require visual or software-based “confirmation”.
3. MSHP Crime Lab Analysis: This is the “gold standard” of evidence. Forensic scientists use Gas Chromatography/Mass Spectrometry (GC/MS) to identify the unique chemical structure and exact weight of a substance.

Upcoming Series: Deep Dives into Evidence

To help you navigate this technical landscape, our subsequent posts will focus on specific categories of evidence found in common Missouri drug cases:

• Field Testing & Preliminary Reports: We will break down the subjectivity of chemical reagents (like NARTEC) and the automated reports generated by mobile apps like MobileDetect.
• The Trunarc Laser Handheld Scan: A look at how Raman spectroscopy works, what a “Type-H” alarm means, and why these scans are often just the beginning of the investigation.
• MSHP Crime Lab Drug Testing. Overview of the Lab.
• Certified Drug Test Results: We will explain how to read a “Certified Report,” including the importance of the reported weight and the 95% coverage probability.
• MSHP Lab Bench Notes and Commo Log: A technical guide to the “backstage” of forensic testing, from TIC abundance graphs to the specific reagents used during confirmation.

By understanding these reports, defendants and their legal teams can identify potential errors, such as sample contamination or breaks in the Chain of Custody, that may lead to a reduction or dismissal of charges.