Law enforcement in South Carolina tests suspected fentanyl in two stages: a quick presumptive test at the scene, then a confirmatory analysis in a crime lab. The field test gives officers a fast yes-or-no signal. However, only the laboratory result reliably proves that a substance is fentanyl. At Eppes & Plumblee, P.A., our drug crimes lawyers see how often the gap between those two stages shapes a drug case.
How Do Officers Screen Substances in the Field?
Field screening, also called presumptive testing, happens at the traffic stop or arrest scene to give officers a quick read on what they found. The result can support probable cause for an arrest, but it is not designed to be courtroom-proof. Screening includes:
- Colorimetric tests that change color
- Handheld spectrometers that scan a sample
- Ion mobility spectrometry (IMS) devices
- Fentanyl test strips (FTS) dipped in solution
Colorimetric kits rely on a chemical reaction that produces a color, while handheld spectrometers and ion mobility spectrometry read the sample’s chemical signature. Each tool is fast and portable, which makes it useful on the roadside but more prone to error than lab equipment. Speed comes at the cost of certainty.
How Do Crime Labs Confirm Fentanyl?
Confirmatory testing is performed at a forensic laboratory using instruments far more precise than those in the field. Analysts typically rely on gas chromatography-mass spectrometry (GC-MS) or liquid chromatography-mass spectrometry (LC-MS), which separate a sample and identify its exact chemical makeup.
South Carolina law, at Section 44-53-190, lists fentanyl and fentanyl-related substances as controlled substances, so the lab must confirm that what was seized actually matches that definition.
What many people do not realize is that a positive roadside field test is only presumptive and cannot, on its own, prove fentanyl in court; South Carolina prosecutors generally need confirmatory lab results, and field tests are well documented for false positives on harmless substances.
Why Presumptive Results Are Not the Final Word
The distance between a field hit and a lab confirmation is where many fentanyl cases are won or lost. Several factors can undermine a presumptive result before a case ever reaches a Greenville courtroom, and a careful defense examines each one:
- Cross-reactions with legal substances
- Operator error during the test
- Poor storage or contamination
- A broken chain of custody
- Missing or delayed lab confirmation
Any of these weaknesses can cast doubt on whether the substance was fentanyl at all. Pressing the state to produce reliable confirmatory analysis, rather than a roadside color change, can reshape or even unravel a charge. The sooner those questions are raised, the better.
Charged After a Fentanyl Field Test in the Upstate?
A field test is only the first step in identifying a suspected controlled substance, and the accuracy of the testing process can significantly impact the outcome of a case.
Eppes & Plumblee, P.A. has decades of combined experience building drug defense strategies in Greenville County, carefully examining testing procedures, chain-of-custody records, and laboratory analyses to identify weaknesses in the prosecution’s evidence. To see where your case stands, call (864) 581-3450 or contact us online.