Unfortunately no. A DWI is a permanent conviction. This is why so many DWI cases go to trial. Your only remedies are both long shots. You can hire an appellate attorney to see if there's any way to get the case overturned on a writ of habeas corpus. Or you can seek a pardon.
It's not considered withholding evidence until after a trial has occurred. What you are talking about is a delay in prosecution. This doesn't affect the admissibility of evidence. This delay is not long enough to get the case thrown out on a speedy trial violation. It is frustrating but not illegal or unconstitutional.
There is no average. You might find one attorney who would do it for a thousand and another who would charge five. Just call a few ticket attorneys in your area. They won't charge you to discuss the facts and give you an estimate.
Absolutely. He needs to ask his attorney to file a speedy trial demand. This should make things move at least a little faster and preserves certain rights on appeal. However, there are risks that come with this approach so he should discuss it carefully with his attorney.
It sounds like he successfully completed deferred probation. This means that no, he has not been convicted. It also means yes, it will show up on a background check. He should be able to seal the record from public view five years from the date he was discharged from the probation. But this only seals the record from public view. Schools will always be able to see it.
The off duty officer had the right to detain you because DWI is a breach of the peace. Whether he had sufficient probable cause to stop you in the first place is a fact specific question your attorney will have to explore after he receives the state's evidence. The streets in a gated community are sometimes considered a public place under the DWI statute and sometimes not. Again, this is a fact specific issue that will probably require a suppression hearing. You need to start interviewing DWI...
Traveling out of the US is not the problem. As you have learned, it is traveling into the other countries that can be difficult. It is up to each specific country whether they grant you admittance, so you would have to contact any country you were planning on traveling to directly.
I advise my clients to dress business casual. Not so sloppy it looks like you're not taking the proceeding seriously, but not so dressed up it looks like you're overselling yourself.
You should make eye contact with the jurors. Be casual, friendly, and appropriate. Don't stare anyone down, but don't avoid eye contact either.
You may not speak to jurors at all. If you run into them in the hall, nothing more than a good morning or a thank you is appropriate. If one of them tries to...