Related Experiment Video
Updated: Jun 26, 2026
10:16
Autoradiography as a Simple and Powerful Method for Visualization and Characterization of Pharmacological Targets
Published on: March 12, 2019
Characterization of postmortem γ-hydroxybutyric acid (GHB) and a novel model to discern exogenous use.
Sue Pearring1, Simone Tchu1, Brigitte Desharnais2,3
1Forensic Laboratory Division, Office of the Chief Medical Examiner, San Francisco, CA 94124, United States.
Journal of Analytical Toxicology
|June 25, 2026
Summary
Interpreting postmortem gamma-hydroxybutyric acid (GHB) is difficult due to natural production and decomposition. A new hybrid model using blood and urine GHB levels improves accuracy in determining exogenous use in forensic cases.
Area of Science:
- Forensic Toxicology
- Postmortem Chemistry
- Drug Analysis
Background:
- Postmortem (PM) gamma-hydroxybutyric acid (GHB) interpretation is challenging due to endogenous production and decomposition-related concentration changes.
- Current guidelines often rely on single criteria like concentration thresholds or urine-to-blood ratios, limiting accuracy.
- A large dataset from San Francisco casework provided an opportunity to develop improved interpretation methods.
Purpose of the Study:
- To develop and validate a novel hybrid model for interpreting postmortem GHB concentrations.
- To improve the ability to distinguish between endogenous GHB and acute exogenous use in forensic investigations.
- To provide a more reliable framework for casework involving GHB.
Main Methods:
- A hybrid model combining peripheral blood GHB concentration (B) and urine-to-blood ratio (U/B) was developed.
- Cases were categorized based on toxicological and investigative findings: acute exogenous use, confirmed exogenous use, or no indication of use.
- The model's performance was evaluated using internal casework data and an independent dataset from Québec, Canada, comparing it against existing guidelines.
Main Results:
- Peripheral blood GHB concentrations in cases with no indication of use were higher in decomposed bodies.
- The hybrid model classified cases into 'no exogenous use,' 'possible exogenous use,' and 'acute exogenous use' categories.
- The hybrid model demonstrated superior performance, particularly in positive predictive value, compared to existing interpretation guidelines.
Conclusions:
- The proposed hybrid model offers a conservative, evidence-based approach for interpreting postmortem GHB.
- This method enhances the distinction between endogenous and exogenous GHB, crucial for forensic casework.
- The model's improved accuracy and validation across datasets support its utility in forensic toxicology.
