Thank you for your question.
Before your brother in law shows up to court, he definitely should talk to a criminal defense lawyer (many criminal lawyers offer free, or low cost, no obligation consultations). First of all, there may be defenses that can be raised -but without talking to your brother in law, a lawyer wouldn't know this.
Even if there are not any defenses that he can raise to the charge, a lawyer can still enter a not guilty plea from on his behalf and then request all the evidence the prosecutor has. Once a lawyer has all the evidence the prosecutor plans to use, he or she can discuss that with your brother to decide what their best approach is - some cases are weak and can be brought to trial; in other cases, it is best to try to negotiate a plea.
Even here, however, a lawyer can be helpful. Criminal lawyers often have established relationships with the prosecutors in each county, know the judges and what to expect in terms of sentencing, and can negotiate a plea that minimizes the charge and/or penalties. It may be possible to plea the OWI to something like disturbing the peace, for example.
Your BIL would be much better off using a lawyer (whether that is a private lawyer or public defender
) than say, simply showing up and pleading guilty without having a lawyer review the evidence. Doing that, he doesn't know what type of sentence he would face, and he may end up getting a harsher punishment than what he might have otherwise.
If you have any follow-up questions, let me know.