Presence Is Not Impairment, and a Number Is Not the Whole Story
A toxicology report can confirm that a substance is present without showing how much, when it was taken, or whether it affected behavior at the moment that matters. Presence and impairment are different questions, and the State often blurs the line between them.
I began my career as an Assistant Public Defender in Florida’s Thirteenth Judicial Circuit, and I am one of only six attorneys in Florida, and just over a hundred in the country, recognized as a Forensic Lawyer-Scientist by the American Chemical Society. On the breath and blood chemistry I am trained in, I read the raw data myself. On DNA, fingerprints, cell-site, digital, and medical evidence, I bring in the right expert and cross-examine the State’s analyst on method, on chain of custody, and on the assumptions hiding inside the conclusion. Learn more about my background.
Reading the Chromatography Myself
As an ACS-CHAL Forensic Lawyer-Scientist trained at Axion Labs, I read the chromatography, the calibration and maintenance records, the chain of custody, and the full lab packet the same way the State’s analyst does. A screening test is not a confirmation, a confirmation has to be run correctly, and the math behind the result has to hold, and that is where many cases come apart.
Where Toxicology Shows Up Beyond DUI
Forensic toxicology drives far more than impaired-driving cases. It reaches the weight and identity of a substance in a drug possession or trafficking case, drug-facilitated sexual assault allegations, overdose and drug-induced homicide prosecutions, and postmortem toxicology, where the redistribution of drugs in the body after death can distort the numbers a jury is asked to trust.
If your case is a DUI, the deepest version of this work lives in my DUI pages on the breath test, the blood test, and drugged driving.
The Lab Packet, Line by Line
The number on a toxicology report is the last step in a long process, and the process is where the answers are. I get the full litigation packet rather than the summary: the screening and confirmation data, the instrument’s calibration and maintenance records, the controls and standards run alongside the sample, the chain of custody, and the laboratory’s standard operating procedures. A result is only as good as the work behind it, and that work is documented in the file the State does not volunteer.
A screening test is fast but presumptive and can flag a substance that is not really there, while the confirmation, usually run on a mass spectrometer, is the test that is supposed to settle it, but only when it is calibrated, controlled, and interpreted correctly. When any of those links is weak, the confirmation is not the final word it appears to be.
Where Toxicology Results Fall Apart
Common failure points include contamination during collection or testing, fermentation in an improperly stored or preserved blood sample, the wrong preservative or anticoagulant in the tube, storage at the wrong temperature, and timing, because a substance found hours later says little about its level at the moment that mattered. In death cases, postmortem redistribution can move drugs through the body after death and inflate the concentration a laboratory measures.
None of this is exotic. It is the ordinary set of things that go wrong in real laboratories, and a forensic toxicologist who reviews the packet with me can show the jury how a number that looked solid does not survive a careful read.
How I Challenge a Toxicology Result
I get the entire laboratory packet, not the summary, test the screen against the confirmation, scrutinize calibration and chain of custody, and bring in a forensic toxicologist where the case calls for one, all under the Daubert standard in section 90.702.
Independent Testing of the Sample
In many cases a portion of the blood or other sample is preserved, which means it can be sent to an independent laboratory for retesting. A second result that does not match the State’s, or that comes back clean, is powerful evidence, and even where retesting confirms the presence of a substance, an independent review can still attack the level reported and what it is said to mean. We look early at whether a sample remains and whether independent testing is worth pursuing in your case.
Common Questions
Does a positive drug test prove I was impaired?
No. A positive result shows presence, not impairment, and not timing. Many substances linger long after any effect is gone, so presence alone does not prove how someone was behaving at the relevant moment.
What is the difference between a screen and a confirmation?
A screening test is a fast, presumptive check that can produce false positives. A confirmation, usually by mass spectrometry, is the more reliable test, but only if it was run and interpreted correctly.
Can a blood or urine result be wrong?
Yes. Contamination, fermentation, calibration problems, a broken chain of custody, and interpretation errors can all undermine a result that looks airtight on paper.
Is this the same as your DUI work?
It overlaps. The chemistry is the same skill set, and my DUI breath, blood, and drugged-driving pages go deeper on the driving context. This page is about toxicology across all criminal cases, not just DUI.
This page is general information about Florida law, not legal advice, and it does not create an attorney-client relationship. Florida applies the Daubert standard for expert testimony under section 90.702, Florida Statutes. The reliability of forensic evidence depends on the methods, the analysts, and the facts of each case, and the science and the law can change, so confirm anything here with counsel about your own situation. Every case is different, and past results do not guarantee a similar outcome.
