As with most traffic items, this will be state-specific. But many states have regulations stating that discovery must be complied with for proceedings to continue. In indiana, the code says that in the traffic cases, the rules of civil discovery apply. These civil rules are very far-reaching as they are the same rules that cover class-action suits, etc. This is a great way to make the wheels of unjustice grind to a halt. I have successfully used a discovery request at the offset to get officers not to show up, get continuances without appearing in court, and to make the prosecution drop charges. Information, like control, is something they do not like giving up. If they see that you will take more effort that the next guy to convict, you have a much better chance. I will post indiana-specific documents and the codes involved. If anyone has information on other states, post that as well.