The Question the State Takes for Granted
Every drug case rests on an assumption: that the white powder is cocaine, that the pills are oxycodone, that the green leaf is marijuana. The arrest report states it as fact. But it is not a fact until the State proves it, and proof means science rather than assumption. Making the State prove the identity of the substance, with a method that holds up, is the part of a drug case the prosecution is least prepared to defend, and it is where my forensic training does the most work.
The Roadside Field Test Is Not Proof
The color test an officer runs on the side of the road, a few drops of reagent in a pouch that turns blue or purple, is a presumptive test only. These kits are known to react to legal substances and to throw false positives, and people have been arrested and jailed on field tests that a real laboratory later contradicted. A field test is enough to make an arrest, and that is all it is. It is not, and was never meant to be, proof that the substance is a controlled drug.
| Roadside field test | Confirmatory laboratory | |
|---|---|---|
| What it is | A presumptive color or reagent test | Definitive identification of the substance |
| Reliability | Known to false-positive off legal substances | Specific identification when done correctly |
| What it proves | Enough to support an arrest | Enough to support a charge at trial |
| Where it is attacked | Cross-reactivity and operator error | Method validation, quality control, accreditation, and chain |
What Real Proof Looks Like
To prove identity, a crime laboratory uses a confirmatory method, and the recognized standard is gas chromatography paired with mass spectrometry. The chromatography separates a mixture into its components, and the mass spectrometer identifies each one by the unique pattern its molecules produce. Done correctly, it is powerful. But the result depends on the analyst, the calibration of the instrument, the validation of the method, and the quality-control data behind the run, and every one of those is something a trained eye can examine rather than take on faith.
The Laboratory Itself: Accreditation and ISO 17025
A result is only as trustworthy as the laboratory that produced it. Forensic labs operate, or should operate, under the international standard ISO/IEC 17025, which sets requirements for technical competence, method validation, calibration, proficiency testing, and documented quality control. When the accreditation is incomplete, the validation is thin, or the quality-control records do not support the run, the identification itself is open to challenge. I read those records the way the lab is supposed to.
Chain of Custody
Identity also depends on continuity. The substance the laboratory tested has to be the same substance seized from the scene, tracked through every hand and every transfer, sealed and logged at each step. A gap in that chain, an unexplained handoff, a broken seal, a missing entry, is a gap in the proof, and it can put the entire result in doubt.
The Drugs-on-Money Trap
In cases the State tries to build around cash as drug proceeds, trace evidence gets oversold. Decades of studies have found that a large share of the circulating United States currency carries detectable traces of cocaine, picked up in counting machines and ordinary circulation. So a positive trace or ion-scan result on money shows that the bills touched the contaminated money supply, not that the person was dealing drugs, a distinction courts have recognized in weighing the limited value of currency contamination. See United States v. $30,060.00, 39 F.3d 1039 (9th Cir. 1994).
How I Use the Science
I treat the lab package as evidence to be read, not a verdict to be accepted: the chromatograms and the spectra, the method validation, the quality-control runs, the accreditation, and the chain of custody. Where the science holds, I tell a client that plainly. Where it does not, the case rarely survives it. This is the same forensic work I bring to a trafficking case, where the identity and the weight of the substance carry a mandatory minimum, and to the broader fight over how the police got the evidence, on the search and seizure page.
Related: Drug crimes overview, Trafficking and mandatory minimums, Marijuana and cannabis, and Challenging a search or stop.
I am one of six ACS-CHAL Forensic Lawyer-Scientists in Florida, with chromatography training from Axion Analytical Labs in Chicago, and I have cross-examined the State’s forensic analysts on how a substance was identified. I read the chromatograms, the mass spectra, and the lab’s own quality records the way the analyst does. More on the forensic lawyer-scientist credential.
Common Questions
How reliable is a roadside drug field test?
Not reliable enough to convict. Field tests are presumptive color tests that are known to react to legal substances and produce false positives. They can support an arrest, but the charge has to rest on a confirmatory laboratory analysis, and that analysis can be examined and challenged.
How is a drug identified in a crime laboratory?
The recognized method is gas chromatography combined with mass spectrometry, which separates a mixture and identifies each component by its molecular signature. The result still depends on the analyst, the instrument calibration, the validated method, and the quality-control data, all of which can be reviewed.
What is ISO 17025 and why does it matter?
ISO/IEC 17025 is the international standard for testing laboratories, covering competence, method validation, calibration, proficiency testing, and quality control. If a lab's accreditation, validation, or quality-control records do not hold up, the reliability of its identification is open to challenge.
What is chain of custody?
Chain of custody is the documented trail showing that the substance tested is the same substance seized, tracked through every transfer and sealed and logged at each step. A break in that chain can put the entire result in doubt.
Does cocaine found on cash prove drug dealing?
Not on its own. Studies have shown that a large share of circulating United States currency carries trace cocaine from ordinary handling and counting machines, so a trace result on money shows contact with the contaminated money supply rather than proof of dealing.
Can a crime lab's drug result be challenged?
Yes. The identification, the instrument data, the analyst's work, the lab's accreditation and quality control, and the chain of custody are all subject to scrutiny. Reading that package the way the analyst does is a core part of a forensic defense.
This page is general information about Florida law, not legal advice, and it does not create an attorney-client relationship. The charge and the defenses turn on the substance, the amount, and the facts, and the law can change, so confirm how it applies with counsel. Every case is different, and past results do not guarantee a similar outcome.
