I couldn't ever imagine making a court submission with hallucinated legal references. It seems incredibly obvious to me that you have to check what the AI says. If the AI gives me a case citation, I go into Westlaw and I look up and read the case. Only then do I include it in my submission if it supports my argument.
The majority of the time, AI saves me a lot of work by leading me straight to the legislation or case law that I need. Sometimes it completely makes things up. The only way to know the difference is to check everything.
I'm genuinely amazed that there are lawyers who don't realise this. Even pre-AI it was always drilled into us at law school that you never rely on Google results (e.g. blogs, law firm websites, etc.) as any kind of authoritative source. Even government-published legal guidance is suspect (I have often found it to be subtly wrong when compared to the source material). You can use these things as a starting point to help guide the overall direction of your research, but your final work has to be based on reading the legislation and case law yourself. Anything short of that is a recipe for a professional negligence claim from your client.