Actually fact-checking an AI requires finding and reading all the precedent yourself to veryify that the AI has both cited accurately and not missed contradictory precedent that is more relevant (whether newer, from a higher court, or more specifically on-point.)

If it has got an established track record, just as with a human assistant, you can make an informed decision about what corners you can afford to cut on that, but then you aren't really fact-checking it.

OTOH, an AI properly trained on one of the existing human-curated and annotated databases linking case law to issues and tracking which cases apply, overrule, or modify holdings from others might be extremely impressive—but those are likely to be expensive products tied to existing offerings from Westlaw, LexisNexis, etc.