Abstract
BackgroundA Drug Influence Evaluation (DIE) is a formal assessment of an impaired driving suspect, performed by a trained law enforcement officer who uses circumstantial facts, questioning, searching, and a physical exam to form an unstandardized opinion as to whether a suspect’s driving was impaired by drugs. This paper first identifies the scientific studies commonly cited in American criminal trials as evidence of DIE accuracy, and second, uses the QUADAS tool to investigate whether the methodologies used by these studies allow them to correctly quantify the diagnostic accuracy of the DIEs currently administered by US law enforcement.ResultsThree studies were selected for analysis. For each study, the QUADAS tool identified biases that distorted reported accuracies. The studies were subject to spectrum bias, selection bias, misclassification bias, verification bias, differential verification bias, incorporation bias, and review bias. The studies quantified DIE performance with prevalence-dependent accuracy statistics that are internally but not externally valid.ConclusionThe accuracies reported by these studies do not quantify the accuracy of the DIE process now used by US law enforcement. These studies do not validate current DIE practice.
Highlights
A Drug Influence Evaluation (DIE) is a formal assessment of an impaired driving suspect, performed by a trained law enforcement officer who uses circumstantial facts, questioning, searching, and a physical exam to form an unstandardized opinion as to whether a suspect’s driving was impaired by drugs
Study selection The International association of chiefs of police (IACP)’s The International Standards of the Drug Evaluation and Classification Program [50], hereafter Standards identifies Drug Recognition Expert (DRE) training as having been “validated through both laboratory and field studies conducted by Johns Hopkins University”
The National College of DUI Defense (NCDD) legal expert identified two studies— Bigelow and Compton—as the those frequently cited in American criminal trials as evidence of DIE accuracy, and a third study—Adler—as being important because it is identified as evidence of the accuracy of DIEs in the official DRE Student Manual
Summary
A Drug Influence Evaluation (DIE) is a formal assessment of an impaired driving suspect, performed by a trained law enforcement officer who uses circumstantial facts, questioning, searching, and a physical exam to form an unstandardized opinion as to whether a suspect’s driving was impaired by drugs. In current forensic practice “Drug Influence Evaluation” usually refers to the combination of the DRE officer’s assessment of the suspect and toxicology testing. This differs from the foundational research, which calculated the accuracy with which officers’ opinions matched toxicology results, and which needed technical terminology for the suspect assessment and officer’s opinion exclusive of the toxicology. This paper will refer to the Law Enforcement Drug Assessment (LEDA) as consisting of two parts 1) the Suspect Assessment (SA), in which data is gathered, and 2) the officer’s DRE Opinion as to whether or not the suspect’s driving was impaired by drugs. The DIE validation studies investigated in this paper calculated the accuracy with which LEDA SAs led to DRE Opinions that correctly predicted toxicology results
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