What Is Idaho's “Excessive DUI” Law and How Does It Work?

Most people know that in Idaho, the legal blood alcohol concentration (BAC) limit for drivers is 0.08%. But fewer realize that Idaho has a separate, more severe classification called “excessive DUI.” This charge applies when a driver's BAC is at or above 0.20% — more than twice the legal limit — and it carries harsher penalties, even for a first offense.

If you live in Boise or elsewhere in Idaho, it's important to understand how excessive DUI works, how it differs from a standard DUI, and what consequences can result from such a charge. Let's break it down.

What Is an Excessive DUI in Idaho?

Under Idaho Code § 18-8004C, an excessive DUI is defined as operating a motor vehicle with a BAC of 0.20% or higher. This is far beyond the legal limit for standard DUI (0.08%) and reflects a level of intoxication considered particularly dangerous.

Excessive DUI can apply even if it's your first DUI arrest — it's the BAC level, not your prior record, that triggers this enhanced charge.

Why Does Idaho Have a Separate Excessive DUI Category?

Idaho lawmakers have recognized that very high levels of alcohol in a driver's system present extreme risks, both to the driver and to the public. Drivers at or above 0.20% BAC typically show:

• Severe impairment of motor skills and judgment

• Inability to react to road hazards or traffic signals

• Increased likelihood of blackouts or passing out

• Greater risk of causing injury or death in a crash

Because of these heightened dangers, the state has carved out a separate category with tougher penalties.

Penalties for Excessive DUI in Idaho

Even for first-time offenders, excessive DUI carries stronger consequences than a standard DUI.

First Excessive DUI (Misdemeanor)

• Jail: Minimum 10 days, up to 1 year (with at least 10 days mandatory)

• Fine: Up to $2,000

• License Suspension: Minimum 1 year (no restricted driving privileges)

• Ignition Interlock Device: Mandatory installation once license is reinstated

• Alcohol Evaluation and Treatment: Required

Second Excessive DUI (Felony)

If you are charged with an excessive DUI and you have a prior DUI (of any BAC level) within the past 5 years, the stakes go up dramatically:

• Felony Conviction

• Prison: Up to 5 years (minimum 30 days of jail time)

• Fine: Up to $5,000

• License Suspension: 1–5 years (with no restricted privileges for the first year)

• Ignition Interlock Device: Mandatory upon reinstatement

A felony conviction can impact your civil rights, employment prospects, and housing opportunities — and it stays on your record permanently.

How Is BAC Measured?

Law enforcement typically determines BAC through:

• Breathalyzer Tests: Often used at the roadside or police station

• Blood Tests: Administered if the breath test is refused or if drugs are suspected

In Idaho, you are subject to implied consent laws — meaning that refusing a chemical test after arrest leads to an automatic 1-year license suspension, regardless of whether you're ultimately convicted.

Excessive DUI vs. Standard DUI: Key Differences

The penalties for excessive DUI are designed to reflect the extreme level of risk associated with highly intoxicated drivers.

Practical Tips: How to Avoid an Excessive DUI Charge

While no one should ever drive impaired, here are some specific points to remember:

✅ Know your limits — BAC can climb faster than you realize, especially with strong drinks or binge drinking.
✅ Use a rideshare or designated driver — If you plan to drink heavily, plan your transportation in advance.
✅ Wait it out — Even after you stop drinking, your BAC can continue to rise for 30–60 minutes.
✅ Remember alcohol tolerance doesn't change BAC — You might feel “fine,” but your blood alcohol content still reflects how much you've consumed.

Final Thoughts

Excessive DUI in Idaho is not just a tougher version of standard DUI — it's a separate legal category with harsher consequences designed to address the dangers of extreme intoxication behind the wheel. Whether it's your first offense or you have prior DUIs, a BAC of 0.20% or higher puts you at risk of severe criminal penalties, long-term license loss, and the lasting impact of a criminal record.

Understanding Idaho's DUI laws can help you make informed, responsible decisions — and avoid turning a night out into a life-altering legal problem. Stay safe, stay aware, and always have a plan before you head out.

If you're facing an excessive DUI charge in Idaho, the consequences are too serious to face alone. Understanding your legal options—and acting quickly—can make a significant difference in the outcome of your case. Boise DUI is here to help you navigate the complexities of Idaho's DUI laws with clarity and confidence. Call us today or schedule a free, no-obligation consultation online to discuss your case and take the first step toward protecting your future.