The experts that I work with (PhDs conducting research in their fields) are easy to tell apart from impostors. Impostors can't accurately cite sources and almost never tell me that they don't know something. Essentially all of the actual experts that I personally work with both cite sources and tell me when they don't know something and sometimes even help me figure out how to find out.
ChatGPT regularly makes up citations out of thin air including DOIs
ChatGPT regularly makes up citations out of thin air including DOIs