Section 708.2A(4) of the Iowa Code criminalizes a third or subsequent domestic violence offense. Assault is defined in section 708.1(2) of the Iowa Code. The Court determined that the definition of assault included "offensive" touching, which was outside the scope of morally turpitudinous conduct. Thus, the Board of Immigration Appeals erred by finding a conviction for recidivist domestic violence was categorically a crime involving moral turpitude.
The full text of Perez Alonzo v. Lynch can be found here: http://media.ca8.uscourts.gov/opndir/16/04/152024P.pdf