If you're suspicious of your spouse and think they may be cheating or you have an inclination to track your spouse, there are certain situations in which it may be legal. Generally speaking, the Texas Penal Code prohibits you from putting a tracking device on the vehicle of another person. However, if you have a vehicle that's jointly owned community property, it is legal for you to put a tracking device on that vehicle, even if your spouse is the one driving it. If you have suspicions about your spouse, it's really best to consult with your attorney about the best means for handling that. To determine whether or not you should put a tracking device, whether it's legal for you're specific circumstance or in some cases, you may decide hiring a private investigator is the safer route to go. But definitely talk to your attorney about those issues and you can determine the best way to handle it for your specific situation.