He may be able to appeal, but his chances of success are probably not very good.
You should speak with a criminal defense attorney that handles appeals.
I am an Austin DWI Criminal Defense Lawyer but I know an appellate attorney I could refer you to if you would like to contact me for their contact information.
Time is of the essence, you must file a notice of appeal very quickly (so do not wait to contact an attorney).
Good Luck.
