How to Challenge a False Positive Hair Drug Result
Facing a false allegation from a drug test result? The steps that actually work.
Last updated
A positive result you cannot account for is alarming, particularly when it lands in the middle of family law proceedings or an employment matter. It is also disputable. A result is a laboratory measurement, and measurements can be checked — against the method used, against your medication history, and against what the number can honestly support.
The most effective step is usually to have the result reviewed by an independent forensic toxicologist.
What a forensic toxicologist can do
Examine the result itself. Which analytes were reported, at what concentration, against which cut-off, and by what method. A screening result that was never confirmed by mass spectrometry does not carry the same weight as a confirmed one, and what the concentration actually means is a question in its own right.
Review your circumstances. Prescription medications, over-the-counter products and diet can all bear on a result. Codeine and poppy seeds, prescribed medicinal cannabis and some common medications each have a documented relationship with particular test results.
Separate use from exposure. A hair result can reflect a drug that reached the hair without being ingested. Distinguishing use from external contamination is a technical exercise involving wash procedures, metabolite ratios and, where the sample allows, segmental analysis.
Provide a second opinion. An independent review of the original laboratory’s work — collection, chain of custody, analysis and interpretation — will establish whether the reported conclusion is supported by the underlying data.
Give evidence. Where the matter proceeds, a written report or expert testimony puts the science in front of the decision-maker in terms they can act on.
Before you make contact
Gather what you have: the laboratory report in full rather than a summary or a screenshot, the chain-of-custody paperwork if you were given it, a list of every prescription and over-the-counter medication you were taking at the time, and the dates that matter to your case.
That material is what a review works from. Without the full report, the first step is obtaining it.
Dr Michael Robertson, forensic toxicologist and chemist
Dr Michael Robertson has more than 30 years in drug and alcohol analysis in Australia and internationally. He holds a Bachelor of Science with Honours in Pharmacology and Toxicology from Monash University and a Ph.D. from the Victorian Institute of Forensic Medicine, and completed a post-doctoral fellowship at National Medical Services in the United States.
He is independent — not employed by the laboratory that produced your result — and fully qualified in clinical and forensic toxicology, a combination that is uncommon in Australia.
His casework spans criminal law, including DUI, drug possession and drug-facilitated crime; family law, where drug and alcohol results are interpreted for the court; and personal injury, medical negligence and workplace disputes. He testifies regularly in courts across Australia, advises national drug testing bodies on policy and compliance with the Australian Standards (AS/NZS 4308:2008 and AS4760-2006), and trains collectors in breath alcohol, urine and oral fluid collection.
Getting a review under way
Expert reports take time to prepare properly, and court timetables rarely move. If you have a hearing date, start early rather than close to it.
Request a consultation or written report, or call us on (03) 9380 5434.
