Consequences For Lawyers Who Fail To Catch Opposing Counsel Relying On AI Hallucinations In Their Legal Briefs

Use Of AI Hallucinations In Court Cases

As readers well know, I’ve been extensively covering and analyzing a myriad of facets regarding the intersection of AI and the law for many years. You can find my writings not only in my Forbes column but also as posted in Bloomberg Law, ABA Law Journal, The National Jurist, The Global Legal Post, Lawyer Monthly, The Legal Technologist, MIT Computational Law Journal, and so on.

I have extensively examined the repercussions for attorneys who have used AI-hallucinated elements in their legal briefs; see my coverage at the link here and the link here. The situation usually is that an attorney opts to include fake legal citations or fictitious quotations about legal cases, having generated those via the sloppy use of generative AI and large language models (LLMs).

I’ve frequently noted that until the courts impose stiffer penalties, or until lawyers wake up and use suitable double-checking procedures and tools, this phenomenon is going to continue. There is a constant drumbeat of lawyers contending they had no idea that AI could produce bad references or bogus quotes. Though this might have seemed plausible when generative AI first hit the scene, the claims of innocence now seem quite hollow. Most savvy attorneys raise their eyebrows when a caught red-handed lawyer tries to plead ignorance of these matters. It does not compute anymore.

Background On The Happenings

Daily bulletins in the legal community keep highlighting lawyers who have used AI to prepare their court filings and ended up with fake legal citations and false quotations in their documents. These errors in legal briefings can potentially occur due to AI hallucinations. An AI hallucination is when generative AI or large language models (LLMs) such as ChatGPT, Claude, Grok, Gemini, CoPilot, Llama, and other AIs veer into generating fictitious confabulations. For my in-depth coverage of AI hallucinations, see the link here and the link here.

I had long ago predicted that attorneys using AI might get careless in their legal efforts and allow the AI to produce bogus content and not double-check by hand what the AI has generated for them (see my prediction in 2023, at the link here).

The problem for attorneys is that when they submit formal court filings, they are supposed to be responsible for the contents of the filings; thus, if AI has slipped in faked citations or false quotations, the lawyer is likely to be held accountable since they didn’t catch the erroneous content. I say “likely” accountable because judges and courts have been quite lenient so far, overall, and allowed excuses such as “the computer did it”. Attorneys often incur nothing more than a minor hand slap or mild rebuke, asserting that AI is new to the legal beagles and they were caught unawares. Sometimes, the reprimands are accompanied by a modest financial sanction or penalty, which is gradually ratcheting up as these instances continue to climb.

Judges and courts are beginning to lessen their patience and sense of charity in giving lawyers the benefit of the doubt. For the time being, the matter is still generally being treated with kid gloves. The expectation is that lawyers are facing a learning curve, and a bit more time is required before they will be able to properly handle the use of AI. In my view, more than enough time has already passed.

Stop coddling legal pros that are supposed to remain on top of the latest technological aspects when performing their legal services (see my coverage of ABA Formal Opinion 512, at the link here, which was promulgated on July 29, 2024, nearly two years ago!).

The Dutiful Double Checking

As earlier mentioned, the expectation is that any attorney worth their salt will double-check the citations and quotes of a filing by the opposing side to their case. This makes abundant sense to do so. If you see a citation or quote that you don’t already know, it behooves you to right away find out about it. Does it help your side of the case, or does it undermine your side of the case?

For those attorneys who know their case law underlying whatever case they are conducting, it should come as a surprise to see quotes or citations that you don’t immediately recognize. Your own experience and homework should have found those previously. That being said, you never know what curveball might come your way. The opposing side might be trying to Hail Mary by using some obscure reference or attempting to shovel an inapplicable consideration into your case. All manner of legal trickery could be afoot.

No worries, just double-check the citations and quotes. There might be important underlying elements that somehow you failed to anticipate. Oops, better get on it right away. At the same time, the opposing side might be playing fast and furious, for which you can potentially pop their bubble and hang them out to dry. There is nothing more rejuvenating than catching the opposing side in a weakness that you can exploit to your side of the case.

Thus, finding AI hallucinations is well worth their weight in gold. It can showcase that the opposing side is lacking in professional aplomb. The beauty too is that if those AI hallucinations serve as a strident foundation for their side of the case, you can kick the pillars and knock down their legal position. Nice.

The added bonus is that it is relatively easy to verify whether the AI hallucinations seem to be based on actual facts. A paralegal can look them up. Does the cited case exist? Yes or no. Do the quotations appear in whatever cited case is being quoted from? Yes or no. Admittedly, you must have sufficient access to online legal libraries, but that’s something an attorney ought to have for their own side of the case to begin with.

Making The Polite Accusation

When an attorney suspects that AI hallucinations are being used in the opposing side’s filing, they cannot be absolutely sure that the AI hallucinations are AI hallucinations. Maybe the opposing side miscopied what they intended to include. Perhaps the attorney on the other side was trying to recite from personal memory what they believed the reference to be or the quotation to be. Perhaps they are still using an old-time typewriter and fat-fingered on the keys. Anything’s possible.

AI might have had nothing to do with it.

In the olden days, before ChatGPT, the odds were that any such mistakes were common human error. I dare say that it was rare in comparison to the frequency of what’s happening these days. Attorneys used to rely entirely on the online records or mountains of legal books they have in their office or legal library. Mistakes of this sort didn’t seem to arise. Briefs were manually typed, checked, rechecked, and had to undergo a litany of scrutiny before getting filed. It has become a push-button operation.

Nowadays, if an attorney catches citation errors and quotation issues, they typically write a polite memo to the other side, inquiring about what they have included in their filing. The aim is not to immediately claim that the world is ending. Don’t want to have egg on your own face. Test the waters and see what the other side has to say.

In addition, the attorney typically notifies the court about the apparently worrisome discrepancies. Again, this is not done boldly. No sense in crying wolf and getting the court to come down on you. Bring it up and remain civil concerning your wide-eyed curiosity about how those citations and quotations came to be.

The Duty Of Attorneys

I am almost to the point of discussing what happens if an attorney fails to uncover that AI hallucinations were filed by the opposing side. Before digging into that realm, let’s set the table a bit further.

Think about the myriad of duties that an attorney has, including these:

• (1) Duty to the court.
• (2) Duty to their professional obligations.
• (3) Duty to their client.
• (4) Duty to adversarial principles.
• (5) Duty to justice.

This is worth dwelling on. An attorney is duty-bound to do their legal work in the utmost proper fashion. According to the “Model Rules of Professional Conduct” by the ABA (excerpts):

• “A lawyer, as a member of the legal profession, is a representative of clients, an officer of the legal system and a public citizen having special responsibility for the quality of justice.”
• “As advocate, a lawyer zealously asserts the client’s position under the rules of the adversary system.”
• “In all professional functions, a lawyer should be competent, prompt and diligent.”
• “A lawyer should strive to attain the highest level of skill, to improve the law and the legal profession and to exemplify the legal profession’s ideals of public service.”

Keep those duties in mind as we venture into the murky terrain of attorneys that falter when it comes to discovering AI hallucinations in the filings of the opposing side.

The Detecting And The Reporting

We need to clarify that there are two key facets to this sobering matter:

• (1) Detection of suspected AI hallucinations.
• (2) Reporting about suspected AI hallucinations.

Here’s why that’s an important distinction.

First, the question arises whether an attorney has some semblance of a duty to detect suspected AI hallucinations.

Do you think they do? It would seem that they must. Their side of the case could be undercut by the AI hallucinations. Anything the opposing side has stated is fair game for attacking your side of the case. To preserve the adversarial system, to ensure you are representing your client sufficiently, to maintain your professional obligations, and so on, it would seem that an attorney ought to find AI hallucinations in their opposing side’s filings.

Of course, as with anything else in the law and the legal profession, there is always the wiggle room factor. It goes like this. If the AI hallucinations are found to be immaterial or inconsequential, perhaps the attorney that ought to have found them is slightly off the hook. It is seemingly a no-harm, no-foul situation. The AI hallucinations didn’t change the game, so it doesn’t merit blaring trumpets.

Another clever angle is to claim to be a victim. The attorney that didn’t find the AI hallucinations takes on the role of a victim that was harmed by the opposing side. Who would have expected them to catch the errors of their opponent? Focus the blame on the side that committed the errors. Keep your eyes askance of the attorney that didn’t catch what the opposing side was up to. Blame the perpetrator, not the victim.

I don’t find either of those postures especially compelling. Just because the attorney got lucky that the AI hallucinations didn’t change the case is not an excuse for having failed to find them. The attorney flatly botched their job. Period, end of story. In terms of being a victim, I find that to be so galling that it is almost impossible not to be repulsed by the posture. Again, this is about their job and the solemn duties as an attorney.

The Detection Question

Whoa, some would say, suppose the attorney did detect the AI hallucinations, but opted not to take any action, which is the second half of two parts involved (i.e., the second part is the reporting of suspected AI hallucinations).

This raises a vital question — why didn’t the attorney take any action to report it?

Aha, the reply comes, because they figured it could be to their strategic advantage for their side of the case. They found the suspected AI hallucinations. Might as well keep this in their back pocket. Later, if needed, spring forth with the claimed AI hallucinations. It might be a saving grace for your side of the case. It could certainly cause a distraction and force the other side into being knocked back onto their heels.

The gist is that the attorney might have seemingly admirably been performing their duties by not reporting the AI hallucinations. You could suggest that by handing over the suspected AI hallucinations, they are principally helping the opposing side. Why do that? Let the opposing side hang themselves. It is your duty to utilize the detected AI hallucinations at the right time and place for your side of the case.

The Reporting

The world isn’t necessarily quite so simple. You could insist that the duty to the court and justice necessitates that the attorney, on a timely basis, bring the suspected AI hallucinations to the attention of the court. Hiding them in a back pocket could be construed as a violation of such duties.

Imagine a judge learning that an attorney knew all along that the opposing side had likely included AI hallucinations. Meanwhile, suppose the judge found the AI hallucinations. The judge asks the parties about the AI hallucinations. Does the attorney who found them now lie and say they didn’t know about them? That’s bad, really bad.

So, the attorney presumably admits they found them, and will have to explain why they didn’t notify the court. I seriously doubt that a judge is going to find it convincing that this was done as a duty to their client. The argument that it was a legal strategy is going to be quite an uphill climb.

One other aspect that will likely get your blood boiling is this. Suppose the opposing side tries to use the fact that the attorney didn’t tell them about the AI hallucinations, or failed to detect them, and thus they are the “victim” and ought to be free as a bird. In other words, attempt to shift the blame away from their mistake and focus attention on the attorney who didn’t, on an adversarial basis, do their job. I know it seems wild, but I fully expect this to be a last-ditch effort to distract the court and toss shade to the other side. Makes your head spin.

More On This Little Discussed Topic

I have more to say about this topic and will be continuing this analysis in an upcoming posting. Stay tuned.

Please go ahead and give these puzzling aspects some mindful consideration:

• Do you think that an attorney who fails to detect and report the use of AI hallucinations by opposing counsel should receive some form of sanctions or penalty by the court?
• What should the sanctions or penalty consist of, and should it be a slap on the wrist or a full-on body blow?
• If an attorney in such a situation opts to hide that they detected suspected AI hallucinations, does this seem like a fair and reasonable use of attorney discretion as part of their legal strategies at play?
• What would you do as an attorney in this kind of circumstance?

Pour yourself a glass of fine wine and ponder these notable questions.

Also, I’d like to acknowledge a LinkedIn posting by Kristina Kalezic that brought up the question of whether there is an obligation to report AI hallucinations associated with an opposing filing. A colleague of mine saw the posting, knew of my prior discussions generally on the vexing question, and suggested that it might be a handy topic for me to do a deep dive on.

The posting smartly mentioned the legal case of Sylvia Noland v. Land of the Free, a California case in the Second Appellate District, which involved a situation of this nature. As per the case: “The AI tools created fake legal authority – sometimes referred to as AI “hallucinations” – that were undetected by plaintiff’s counsel because he did not read the case the AI tools cited” (quoted from the appeal response filed September 12, 2025).

In my next analysis, I will go into depth about the case and explain what the court decided to do about this. I close for now with one of my favorite quotes by Abraham Lincoln: “The leading rule for the lawyer, as for the person of every calling, is diligence. Leave nothing for tomorrow which can be done today.”

Truly wise words, especially in an era of AI hallucinations and legal discourse.