First, a judge can order you to install a breath device on ANY CAR YOU DRIVE. If you can prove you do not drive the second car, then the order should be rescinded.
Second, a judge (depending on his or her ethics) can order anything they want to and get by with it.
Third, this is why you need a qualified DWI defense lawyer to be your protector. Above, click on the tab, "Find a Lawyer". You can also go to TCDLA.com to their lawyer locator for a DWI specialist. Then interview a few to see who you can work with. Good luck.
You haven't given enough information to allow a definitive answer, and it would involve a lot of information. The judge responsible for your case, and thus for overseeing the bond you are out on, has a lot of discretion. Short answer is that it's probably legal, and you don't have much choice. In terms of pursuing this issue, which has no bearing on your case, the best you could hope for is getting the IID removed from your wife's car, and even that would be difficult to accomplish.
This answer is intended to be taken as general information and not as specific legal advice. You should always consult a qualified attorney and make him familiar with all the relevant facts in order to get proper legal advice. Every case is different, and they must be evaluated on a case-by-case basis. David N. Smith 812 W. 11th Street, Suite 201 Austin TX 78701 (512) 457-0100 defenseattorneysmith.com
It's typically ANY car you drive, especially on a bond condition.
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