NOT A TEACHER
See definition #2 here.
Student or Learner
Policement told the suspect "You got a lot of nerve. Maybe I got you pegged all wrong. Maybe you are a kidnapper."
What does "got you pegged" mean? Why can't I find it in the dictionary? Got a lot of nerve means the suspect has guts?
Where is this from? I haven't met this expression, but it seems to me that it might mean something like 'I had been thinking that you were a bank-robber [and so, put you - mentally - on the 'peg' marked 'Bank-Robbers'], but maybe I should move you to my (mental) 'Kidnappers' peg'.
But as I said, this would be a new one for me. I've chiefly met the verb 'peg[ged]' in the phrasal varb 'to peg back'.
It's fine in BrE too. "I had you pegged as an animal lover but then I saw you eating veal!"
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.
Please be aware that I'm neither a native English speaker nor a teacher.
"Pegged" also refers to the needle on a speedometer being at its maximum reading (literally hitting the peg in the gauge).