By Dr. David Lehmann
Why the Definition of “A Drink” Matters
When someone says, “I only had two drinks,” it sounds simple. In alcohol-related enforcement and litigation it rarely is.
In DUI investigations and dram shop cases, the phrase “a drink” gets used constantly. Officers document it. Attorneys rely on it. Experts analyze it. Jurors hear it.
But what exactly is a “drink”?
Is it a bottle? A glass? A shot? A pint? A cocktail? Before a toxicologist can evaluate impairment, timelines, or service practices, the more basic issue has to be addressed first: What does that person actually mean by “a drink”?
When Drink Counts Drive the Case
Alcohol cases often hinge on quantity and timing. How much was consumed? Over what period? What level of impairment would reasonably be expected?
If the foundation – the drink count – is unclear, every downstream analysis must account for that uncertainty.
Three “beers” could mean:
Three 12 oz light lagers at 4.2% alcohol by volume (ABV)
Three 12 oz standard beers at 5% ABV
Three 16 oz craft IPAs at 8% ABV
Three 12 oz double IPAs at 9 to 10% ABV
Or something else altogether
Those scenarios involve different amounts of alcohol (i.e., different exposures). The phrase “a drink” deserves more scrutiny than it often gets.
What Is a Standard Drink?
In toxicology, dose is a fundamental principle – the effect of a substance is determined by the specific amount that enters the body. In the context of alcohol, we measure this dose using the “Standard Drink” concept.
In the United States, a standard drink contains about 14 grams (0.6 fluid ounces) of pure ethanol (i.e., alcohol). That corresponds to:
12 oz of beer at about 5% ABV
5 oz of wine at about 12% ABV
1.5 oz of distilled spirits at 40% ABV (80 proof)
These are alcohol-content equivalents – not container equivalents.
A 12 oz beverage is not automatically one drink. Neither is a glass or a shot. The only thing that defines a standard drink is the amount of pure alcohol it contains. The baseline matters – especially when drinking histories or reconstruction opinions rely on it.
A Beer is Not Just a Beer
Years ago, assuming that “a beer” meant a 12 oz, ~5% ABV product was often reasonable. Today, that assumption is less reliable. Beer sizes range from 8 oz “stubbies” to 32 oz “growlers.” Alcohol content commonly ranges from 4% to 10% – and specialty products exceed that.
A 16 oz pint at 8% ABV contains roughly 2.1 standard drinks. Three of those? Now we’re above six standard drinks – even though the person may describe it as “three beers.”
That difference can materially affect dose reconstruction and impairment analysis.
Wine and Spirits: Same Issue, Different Form
The standard drink model assumes:
5 oz of wine at ~12% ABV
1.5 oz of distilled spirits at 40% ABV (80 proof)
In practice:
Restaurant wine pours often exceed 5 oz
Wine ABV may range from 11% to 15%+
Fortified wines are substantially higher
A 9 oz pour of 14.5% wine can exceed two standard drinks. So “two glasses of wine” could represent two drinks — or four or more.
Spirits present similar variability.
A 1.5 oz pour of 120-proof whiskey contains significantly more alcohol than an 80-proof pour. Add double pours, free pouring, or cocktails built with 2–3 oz base spirits, and “one drink” may represent far more alcohol than assumed. An Old Fashioned made with 2 oz of 100-proof bourbon exceeds one standard drink. Most patrons would still call it one.
The body processes ethanol the same regardless of source. But serving size, proof, and drinking pattern can vary widely — and that variability matters.
Why This Matters Investigatively
When documenting alcohol consumption, details reduce uncertainty.
Instead of:
“Subject stated she drank three beers.”
More useful information would include:
Brand and ABV
Container size
Draft vs. bottle/can
Time period of consumption
Food intake
Spirits or mixed drinks
Whether drinks were shared
Specificity collected early reduces speculation later.
The Central Point
In alcohol-related cases, “a drink” is often treated as a unit of measurement. It isn’t. It’s a description — and frequently an imprecise one. Before evaluating impairment, timelines, or service practices, the better question is:
What does that person mean by a drink?
Because when alcohol exposure is at issue, small definitional differences can meaningfully influence how the evidence is interpreted.
Disclaimer: All views expressed here are my own and do not reflect the views of my employer or any affiliated organizations or partners.
