Hire a lawyer to represent you and be sure to keep the photos. There are many excellent lawyer who handle DWI cases in Harris and Ft. Bend counties. Right now, you should take no action with regard to the beating until you have consulted with your criminal lawyer. And, you need to consult with your criminal lawyer ASAP as there are time limits with regard to relevant driving matters.
I agree with Cynthia's advice and only add in that you need to write down everything that happened that night while it is still fresh in your mind. You may end up filing a complaint with the arresting agencies Internal Affairs Detail but let the attorney you hire help with that call. Time is of great importance so get busy.
Your situtation raises a host of issues. As regards the allegation of DWI, it is critical you seek the representation of a criminal attorney who can guide you through the myriad of legal venues you will need to travel to protect your driver's license and to defend yourself against the allegation of DWI. You have only 15 days from the date of arrest to challenge the State's intention to suspend your driver's license. Additionally, Texas law allows for increased sanctions and penalties depending on whether a breath or blood test is refused. As regards your mistreatment by the police, it is important you maintain all of the evidence you can and make attempts to hold accountable those officers who were involved. You will likely be best served by an attorney with extensive experience in criminal law as well as internal affairs investigations.
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