The correct spelling of this expression is “scot-free”. “Scotch free” is incorrect in English and should not be used.
To get off scot-free
The expression to get off scot-free means that you don’t have to pay any punishment for something that you have done. It is an expression that came from medieval England which meant that you didn’t have to pay a tax.
I believed he killed his wife but he got off scot-free.
What? He didn’t have to pay tax! He got off scot-free.
“Scott-free” is an incorrect spelling of “scot-free”. This is a common mistake because of the name “Scott”.