It is, but only partially. When a person is charged with DUI, their case will be decided on its merits.
In a criminal case, there are three potential defenses; two are factual, and one is a legal defense.
Factual Defenses to DUI:
The first and most obvious argument is innocence, which needs no discussion.
The second defense is justification. In a justification defense, the accused must admit to committing the crime yet should not be convicted due to a sufficient reason. The most commonly used justification defense is self-defense.
In DUI, justification most often happens when someone is forced to flee, using their vehicle to escape danger. That can occur in a domestic violence situation or even fleeing a bar fight.
Legal Defenses to DUI:
Legal defenses are the result of when a police officer violates the constitutional rights of the accused, usually through a violation of police procedure. If a police officer violates a person's rights, the State cannot prosecute that person.
That is where mistreatment can come in. In and of itself, mistreatment does not constitute a perfect defense. A person can be guilty of DUI, and at the same time, a police officer can be guilty of abuse.
However, if the mistreatment is severe, it is unlikely that the court will find him a credible witness or a prosecutor will want to use the officer as a witness. That being said, the fact that someone was mistreated does not mean their case will automatically be dismissed.