Knowing the standard rules for if clauses I have always wondered whether some speakers just use the if part as if (no pun intended) it were a non-conditional sentence.
I am just watching a movie and have the following example:
If you knew then why did you...
where the speaker finds out that the other person had known that the victim was innocent but still punished him despite this knowledge.
So obviously both things happened in the past - not only grammatically but actually.
When is this non-standard form used? Is it informal? Is it American English (they sometimes say things like "If I would..." and this is also an American movie)? And how is this form called grammatically?