I've finished writing and testing a PHP script to import an XML file (validated against http://web.uvic.ca/~lang02/bailey/schema/bailey_trialfile_proofing.rng ) into the MySQL database. The script using SimpleXMLElement to load and loop through the file. The database handling is done by Zend_Db, since that's already being used in the main Bailey website.
I wrote the importer in such a way that new foreign keys (e.g. crime_normalizeds, judges, etc.) don't need to be entered into the MySQL database beforehand. Since the XML is validated against the schema, I can be reasonably certain that all of the values in the data are intentional. So, if the importer comes across a value that's not already in the MySQL database (say, a new judge), it simply inserts that value and continues with the import.
The importer isn't yet online, but once it is I'll publish its URL to this blog.