The most frequently used technical evidence in drug cases are urine and hair tests. The technical features of these tests, the conditions for their acceptance as evidence and "false positive" objections are the subject of this article.
Urine Test — Window Period
- Cannabis (THC): 3-30 days (depending on frequency of use).
- Cocaine: 1-4 days.
- Heroin/morphine: 1-3 days.
- Methamphetamine: 1-4 days.
- MDMA: 1-3 days.
- Synthetic cannabinoids: May not be detected in standard panels; special testing required.
Hair Test — Looking Back
Hair test allows retroactive detection up to 90 days, thanks to the growth rate of the hair (approximately 1 cm/month); In some cases, it provides information up to 6 months in advance. A total of 3-4 cm is taken from the tip of the hair; Each cm shows a different period.
"False Positive" Risks
- Some prescription drugs (e.g. amphetamine-derived prescription drugs) may give a positive result on the test.
- Herbal products and foods (poppy seed bread, some tablets/syrups).
- Passive exposure (intense marijuana smoke environment) may produce suprathreshold results in some cases.
- External contamination in hair testing (extended exposure to marijuana smoke).
Confirmatory Test (GC-MS / LC-MS)
Rapid screening tests (immunoassay) are only "preliminary screening". Forensic standard: a positive result must be confirmed by GC-MS (gas chromatography-mass spectroscopy) or LC-MS (liquid chromatography-mass spectroscopy). An unverified result is weak evidence in court.
Supreme Court 10th CD — Principle
10. CD, urine and hair tests can be used for conviction, provided that they are collected properly, the chain of evidence is preserved, confirmatory analysis is performed and the report is obtained from an independent laboratory; It is accepted that the pre-screening test alone is insufficient.
Defendant's Objection Rights
Forensic files should be handled with expert support. Drug crimes lawyer recommended.