Retrospective Study on the Power and Interpretation of Chiral Amphetamine Analysis in Hair for Forensic Applications.

Chiral amphetamine analysis is performed in forensic toxicology to determine the nature of amphetamine intake (therapeutic or illicit). It is crucial to the correct interpretation of amphetamine-positive hair samples in terms of abstinence control and therapy compliance, where hair analysis is used to evaluate the average amphetamine use over a period of several months. However, interpretative challenges arise when different medication intakes and/or illicit drug consumption events contribute to the hair analysis result. Therefore, a retrospective study of authentic casework was conducted (2017-2025, n = 340) to assess the performance of chiral amphetamine analysis in hair and to enhance the interpretation of its results. Two liquid chromatography tandem mass spectrometry (LC-MS/MS) based methods were used and compared, based on chiral derivatization (i.e., indirect method) or a chiral stationary phase (i.e., direct method). Chiral analysis results are expressed as enantiomeric fractions (EF) of (S)-amphetamine in hair. Chiral analysis results in hair were interpreted as in accordance with therapy compliance (e.g., Elvanse or Attentin) (EF ≥ 0.95, n = 284) or illicit amphetamine use (EF ≤ 0.55, n = 32). Between these proposed cut-offs, the results were indicative of combined use of medical and illicit amphetamine or of therapeutic use of mixed amphetamine salts products (e.g., Adderall) (0.55 < EF < 0.95, n = 24). It was shown that segmented hair analysis can be beneficial for the interpretation of such indicative results. This retrospective study shows that chiral amphetamine analysis in hair confidently distinguishes between (sole) therapeutic and (sole) illicit amphetamine use and has established a decision model for the interpretation of EFs in hair for forensic casework.