The “Hip Flask” Defence — Why It Rarely Works and Might Get You Convicted Twice

Stop asking ChatGPT for legal advice. It might get you into bigger trouble

The “Hip Flask” Defence in Ireland – Why It Rarely Works

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“But I only had a drink after I parked…”

If you've been charged with drink driving in Ireland, you might be tempted by what sounds like a clever loophole: Tell the court you had a few drinks after you parked the car—but before the Garda breathalysed you.

Some people even get this idea from ChatGPT. One of my clients told me he relied on advice from it. From talking to colleagues across the country, it’s repeatedly being suggested by desperate clients. ChatGPT seems to be the culprit.

They think it might work. It won’t.

And if you try it, you could make your case much worse.

"this is a reverse burden of proof.

You have to bring the evidence,

and the court doesn’t even have to

consider your version unless it’s backed up"

What is the “hip flask” defence?

The “hip flask” defence is a legal argument where someone claims they were only over the limit because they drank alcohol after driving—but before being tested by Gardaí.It takes its name from the flasks people used to carry alcohol discreetly, often used in the US during the Prohibition era.

It sounds simple enough. But legally, it’s incredibly difficult to prove—and today, the odds of it succeeding are very low.

The law in Ireland: Section 18 of the Road Traffic Act 2010

This defence used to shift the burden to the prosecution to disprove what you said. That’s no longer the case.

Section 18 of the Road Traffic Act 2010:

• The prosecution does not have to prove that you didn’t drink after driving.

• Instead, you must prove that “but for” the drink you had after driving, your alcohol reading would have been under the legal limit.

As summarised by David Staunton in his leading textbook Drunken Driving (2nd ed., 2021, pp. 58–60):

“The onus is on the defendant to show that the intoxicating liquor consumed rendered him or her over the prescribed limit… The court shall disregard the evidence unless satisfied that ‘but for that consumption’ the concentration of alcohol… would not have exceeded the prescribed limit.”

In short: this is a reverse burden of proof. You have to bring the evidence, and the court doesn’t even have to consider your version unless it’s backed up.

"the court later remitted the case for conviction

after finding the defendant’s explanation

inherently unlikely"

What you’d need to prove

To succeed with the hip flask defence, you’d need to show—probably through expert evidence—that:

• You drank after the driving,

• That this post-driving alcohol is what pushed you over the limit, and

• That without it, your alcohol reading would have been below the threshold.

According to case law such as DPP v Dukolli [2009] and DPP v Bolton [2009], courts have consistently held:

“Except in rare cases where it is unnecessary, it has been the standard practice for many years for defendants to call medical or scientific evidence when running a hip flask defence if they are to stand any real chance of success.” — (Openshaw J, in Dukolli).

Even in Dukolli, where no expert evidence was initially provided, the court later remitted the case for conviction after finding the defendant’s explanation inherently unlikely.

That’s because without expert support, the defence rests entirely on your credibility—and courts are deeply sceptical.

Judges have heard it all before

Judges are not easily persuaded by:

• “I was in shock after the crash, so I took a sip of vodka.”

• “I only drank to calm my nerves.”

• “I had one small mouthful as the Garda approached.”

In R v Durrant [1970] and Rowlands v Hamilton [1971], the courts made it clear that the burden to raise and support this defence lies with the accused—not the prosecution.

The issue isn’t just whether you drank—but whether your explanation is plausible, consistent, and supported.

If you told Gardaí one version at the scene, and now you're telling a different one in court?Your credibility is gone. And your defence goes with it.

Worse still — you could face a second conviction

Section 18(3) of the Road Traffic Act 2010 creates a separate offence:

“A person shall not take or attempt to take any action… including the consumption of an intoxicant… with the intention of frustrating a prosecution.”

"[Chatbots] don’t understand how Gardaí operate,

how judges weigh credibility, or how evidence,

caselaw or legislation are interpreted in Irish courts"

As David Staunton puts it:

“The provision is very broad and is designed as a catch-all to cover all types of mischief imaginable… a defendant who places reliance on the hip flask defence may be convicted of an offence under this section.”

Alarm bells should now be ringing.

This means if the court believes you drank after driving to try and manipulate the test result, you could be:

• Fined up to €5,000,

• Sentenced to up to six months in prison, or

• Both—in addition to any penalty for drink driving.

What ChatGPT gets dangerously wrong about this defence

You might have searched online and found that ChatGPT or another AI tool says the hip flask defence could work.

That’s exactly what one of my recent clients did. He asked ChatGPT about his drink driving charge, and it suggested he might avoid conviction by claiming he drank after he drove.

But here’s the problem:

·       That advice ignored Irish law completely.

·       It doesn’t have access to core legal precedents or important decisions

·       It failed to mention Section 18 of the Road Traffic Act 2010, the reverse burden of proof, and the serious risk of a second criminal charge for frustrating a prosecution.

AI tools don’t know the details of your case.

They don’t understand how Gardaí operate, how judges weigh credibility, or how evidence, caselaw or legislation is interpreted in Irish courts.

They can’t account for:

• Your statements to Gardaí at the scene,

• Important legal judgements

• Whether you’re even considered a credible witness.

Worst of all? Once you’ve told Gardaí one version of events, it’s too late to rewrite your story around what you’ve read online.

Relying on ChatGPT in a drink driving case is like taking medical advice from a chatbot after you’ve broken your leg. It might sound confident—but it’s not responsible, accurate, or safe.

Focus your energy where it matters

If you’ve been charged with drink driving, it’s natural to want a way out.

But grasping at online myths or loopholes won’t help you.

What will help?

• Understanding the legal proofs required for a conviction,

• Examining Garda procedure to see if it was correctly followed,

• Identifying whether the evidence meets the legal proofs required in court, and

• Working with someone who knows how to find real defence points in the case.

Because at the end of the day, trying to game the system could cost you everything—including your credibility, your licence and maybe your job.

"Relying on ChatGPT in a drink driving case

is like taking medical advice from a chatbot

after you’ve broken your leg.

It might sound confident—

but it’s not responsible, accurate, or safe"

Think carefully about what you read online.

Always apply critical thought.

Focus sensibly on your case.

After all, everybody wants to drive home, right?