Intelligence Squad members are often seen talking on their cell phones as they're racing to a crime scene. This is illegal in many states, Illinois included. It's also extremely unsafe, as the drivers are usually driving while in pursuit or racing to a scene.
Police officers consistently say a person was DOA, which stands for Dead On Arrival (at a hospital), when the person is found dead at the scene of a crime. What they should say is DOS, which stands for Dead On Scene. However, while DOA can mean 'found to be dead upon arriving at hospital', it can also mean 'found dead at a scene, upon the arrival of an emergency medical service, or the police or other qualified first responders'.
Even in the most corrupt police department in the United States, the types of antics seen in the Chicago squad would draw quick and immediate investigation and prosecution from all manner of authorities. Hank and his team are routinely seen beating confessions out of suspects, planting evidence, and frequently continuing interrogations in a basement cage room even after people ask for a lawyer. Evidence is also frequently planted and squad members are seen lying in court to secure convictions. There are also several references to Hank having suspects quietly killed to avoid the chance of them being released. All of this behavior is never questioned by anyone and apparently tolerated by the Chicago police leadership.