In Hamishi of Vayiqra we see three cases of sin/error:
A. A Kohein Gadol who sins/errs.
B. The entire congregation -or as per Hazal the Sanhedrin - but perhaps BOTH understandings apply.
C. A Nassi.
In Sh'mini, Moshe apparently renders an incorrect hora'h and is corrected by his brother Aharon.
Who - I.E. what individual - in Judaism is infallible?