Consideration of a per se law for driving under the influence.

Mapp, Richard C · 1980 · ROSA P / Virginia Transportation Research Council (VTRC)

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Summary

This 1980 report by Richard C. Mapp, prepared for the Virginia Highway and Transportation Research Council, evaluates the potential adoption of a *per se* law for driving under the influence (DUI) in Virginia. The study was motivated by a legislative inquiry into whether Virginia Code §18.2-266 should be amended to prohibit driving when blood-alcohol level (BAL) exceeds a specified limit, rather than relying solely on the subjective standard of being "under the influence." The report aims to assess the impact of such a change on prosecution, enforcement, and deterrence, addressing the fact that alcohol impairment is the largest single factor in fatal traffic accidents. The analysis relies on a review of medical research regarding the correlation between BAL and driver impairment, an evaluation of the accuracy of chemical testing methods used by Virginia law enforcement, and an examination of the existing legal framework. The author reviews studies demonstrating that driver skills significantly deteriorate and accident involvement rates increase at BALs of 0.08% or higher. The report also critiques the current evidentiary standards, noting that while Virginia law presumes guilt for BALs of 0.10% or above, this presumption is rebuttable. Consequently, prosecutors must provide corroborative police testimony regarding observed impairment, which complicates convictions and contributes to lax enforcement. The findings indicate that a *per se* law, which would make a BAL of 0.10% or above conclusive evidence of intoxication, would eliminate the need for corroborative police testimony and prevent defendants from rebutting the presumption based on claimed tolerance or lack of observed impairment. This change would likely increase conviction rates, expedite plea bargaining and referrals to alcohol rehabilitation programs, and ensure greater uniformity in the treatment of offenders across state lines. The report addresses opposition arguments regarding deterrence, constitutional rights, and vagueness, concluding that while empirical evidence for deterrence is mixed, increased enforcement and public awareness resulting from stricter laws are probable. The significance of the report lies in its recommendation to amend Virginia’s DUI statutes to include a *per se* provision. The author concludes that such a law would simplify prosecution and enhance highway safety. Specifically, the report recommends advancing a proposal that makes driving with a BAL of 0.10% conclusively illegal and driving with a BAL between 0.08% and 0.10% presumptively illegal. This approach balances the administrative ease of a *per se* law with the safety benefits of lowering the threshold for presumed impairment, while allowing for rebuttal in cases of physiological tolerance.

Key finding

A per se law prohibiting driving with a blood-alcohol level of 0.10% or above would eliminate the need for corroborative police testimony on observed impairment, thereby increasing conviction rates and potentially deterring drunk driving.

Methodology

review

Provenance

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Topics

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• dui enforcement
• drowsy as impairment
• alcohol
• alcohol detection systems