The website of the Office of Immigration Statistics has a lot of information that would be useful to your search. Specific to the issue of deportations and domestic violence, you can find the number of people deported who are classified as "criminal" by category in this document:

Immigration Enforcement Actions 2004

It's a link on the Office of Immigration Statistics web site, publications page.
Office of Immigration Statistics: Publications

Within this document, look for Table 4 on Page 6. It's entitled "Removal of Criminal Aliens by Leading Crime Category:2004" and it lists percentages as well as numbers of people deported within
crime categories cited as reasons for deportations/removals.

The one that seems to fall closest in area to domestic violence is family offenses. Other categories listed include sexual assault and sex offenses.

The source listed for the data is the "Deportable Alien Control System."

For more data on deportations, including state by state data, try the Yearbook of Immigration Statistics. It's available online, but if you live near a librarythat's a gov doc repository, you might be able to find a print copy there too (do a title search under Yearbook of Immigration
Statistics).

The link for the Yearbook of Immigration Statistics, 2004 is:

Yearbook of Immigration Statistics