We've learned the L.A. City Attorney has contacted the NYPD for all their info on that Kiefer Sutherland headbutting incident last week.

Kiefer is on probation for a DUI conviction in L.A. One of the conditions of probation -- he must obey all laws. The City Attorney could go back to the judge and ask that Kiefer's probation be revoked and that could potentially mean some serious jail time -- around 11 months max.

The City Attorney hasn't made a decision yet.