The above link is to the text of the new hands free ordinance that went into effect January 1, 2015.
Here are what I believe are some notable points:
(1) This appears to ban all cell phone use, however you are allowed to turn your phone off and on if using a hands free device.
(2) This appears to state that if using a hands free device, it must be completely hands free (including the dialing process). So, theoretically, if you are searching for a number on your phone to dial on your hands free device, you are in violation of this ordinance.
(3) It does not matter if you are stuck in traffic or stopped at a light or stop sign, you cannot use your phone, unless hands free.
(4) The ordinance appears to allow you to use your phone for GPS/ mapping purposes, however the phone would need to be attached to the vehicle in some way.
(5) This is a city of San Antonio ordinance, which means this only effects violations within the city of San Antonio.
(6) This is a class C misdemeanor, which means there is no jail time. The fine is up to $200.
(7) For the first 30 days of 2015, only warnings will be given.
(8) There are exceptions for emergencies, etc.
Practically speaking, these cases will likely be prosecuted very similar to the way any other traffic violation is prosecuted. In these cases the officer will testify to what he observed, and the defendant will have a right to offer his explanation. One person's word against another. Typically that's all there is to prosecuting these types of cases. Although text messages and cell phone records are potentially admissible, these cases usually do not get that involved.
Aside from the criminal aspect, it will likely have some impact on personal injury cases as well. Cell phone use and distracted driving is very often the the cause of automobile accidents and deaths. Many claim, probably correctly, that distracted driving is an epidemic. The cause of action for these types of civil cases is generally negligence. In proving negligence, the driver generally has to show that the defendant had a duty to drive in a safe manner, the defendant breached that duty, and that breach caused damages to the plaintiff. In a trial where negligence is alleged, if it can be proven that the defendant was breaking the law, it constitutes what's called negligence per se. This is a doctrine in the law, which essentially means, if you can show that the defendant was breaking the law when they caused injury to another, then it creates a rebuttable presumption they are negligent.
Although it helps if the negligent driver was cited or ticketed for the violation by law enforcement, I don't believe that this is absolutely necessary to open the issue of negligence per se up to the court. However there needs to be some evidence that the negligent driver was in violation of the law (witness, cell records...).
