A woman I interviewed brought in a stack of notes. She had a set of pre-prepared scenarios for each competency she'd be asked about - 24 pages with little post-it tabs so she could quickly find an answer to most of the questions we asked.
Her answers were impeccable until she was asked a question that she didn't have an answer written down. She stumbled through for a minute then I prompted her by saying - just think of the scenario you talked about for question 2 relating to xxx. That example could be used here.
She couldn't remember the answer she gave, nor the scenario she based her answer on.
Basically, her scenarios were made up, she did not have the experience required and had received loads of help in the interview prep stage to come up with 24(!!!) answers.
In that particular case, she was simply cheating.
With a bit of luck she'd have breezed through that interview and taken a job she wasn't qualified for, and someone who did deserve the job would lose out. Not only that, how she was planning to do the job once she was in role was beyond me!
Now I don't allow notes in interviews.
To the PP who said an interview is not a memory test, I agree. It's a conversation about things you've done. If you can't remember what you've done in the past, how can you apply them to a new role?