All you can do is an open records request... but if it is an open case, there is still alot of information they will not provide to you until the case is closed. You must go through a lawyer.
I agree with the answer posted above. An ongoing criminal investigation (and all criminal cases are ongoing investigations) is an exception to the Texas Open Records act. Therefore, you need to go through a lawyer to get the information you seek.
The information provided above is for informative purposes only. You should hire your own lawyer to get specific legal advice regarding your situation.