Then they tell you the previous person was incompetent or something to try and make it seem like they were a bad employee, not that it's a bad work environment.
"Oh? And who was in charge of their interview?" because unless they have a large hr department to handle hiring interviews, it was probably the person who hired you.
This is when you take notes in your notebook you should have brought with you.
I've noticed interviewers get visibly uncomfortable when I write in my notebook. It's like they're either trying to figure out if they just lied about something I will be able to reference later, or they just get that natural "someone is writing about me and I can't read what it is" feeling, I assume the former.
Simon Pegg wasn't lying in Hot Fuzz. The notebook is a powerful weapon if used right.