Criminal investigations are typically carried out in two phases: pre-arrest and post-arrest. Pre-arrest investigations can be simple investigations conducted on-scene by an officer, or they can be long and detailed investigations conducted by detectives. Post-arrest investigations are generally conducted by investigators working for the prosecuting attorneys.
Here is an example of a simple pre-arrest investigation. When an officer conducts a traffic stop, he is trained to also conduct an investigation and look for signs and evidence of criminal activity. When the officer is asking you questions related to the traffic stop, he is also looking for signs of intoxication, the smell of alcohol or marijuana, or any other clues of criminal activity. If the officer doesn't see any signs of criminal activity, he will conclude his investigation and wrap up the traffic violation for which you were stopped. If the officer does see something that he believes indicates a possible criminal violation, he will investigate further. For example, if he suspects the driver is intoxicated, he may have the driver exit the vehicle and conduct standardized field sobriety tests.
Other pre-arrest investigations are much longer and more involved. They may involve multiple government agencies, surveillance of suspects, and interviews with several witnesses and sources of information. With this type of investigation, it is possible that you may not even realize that you are the target of the investigation. Most people think that if they haven't done anything wrong, there is no way they can be under investigation for a crime. Unfortunately, that is not true. Innocent people are arrested every day in Texas. If a law enforcement agent wants to speak with you, it is important to consult with a criminal defense attorney before answering any questions. If you are the suspect in a crime, law enforcement officers are trained to gather evidence to support your arrest and conviction. They are not trained to be objective and to protect your interests.
Texas law requires you to give your name, date of birth, and residence address to an officer if you have been lawfully arrested and the officer requests this information. (Texas Penal Code §38.02.) Other than that requirement, you do not have to answer questions. However, it is important to consider that not cooperating carries its own set of risks. Not answering questions will keep officers from hearing your side of the story. It will most likely make them angry and can cause them to respond more harshly than they otherwise would have. And if the case goes all the way to a jury trial, it can make you look bad in front of a jury.
So you find yourself in this position... If you answer their questions, everything you say can be used against you. But if you refuse to answer the questions it makes you look bad. And that's where having an attorney representing you comes into play. Your attorney can give the investigators your side of the story without the risk of having a prosecutor twist your words in the future at trial. This also prevents you from being seen as being completely uncooperative by both the investigators and the jury.
We've all seen the, "You have the right to remain silent. Anything you say can and will be used against you..." warnings on television. These warnings are required before police can interrogate a suspect in certain situations. They are called Miranda warnings because the requirement for these warnings comes from a case called Miranda v. Arizona which was decided by the Supreme Court in 1966.
It is a common misconception to think that your statements cannot be used against you if the police didn't advise you of your Miranda rights before questioning you. However, officers are only required to advise you of your Miranda rights if they are asking you questions while you are in custody. If they call you on your cell phone and ask questions they can use your answers against you and do not need to advise you of your rights. The same goes for them asking you to come to the police station and talk. If you can leave, then they don't need to Mirandize you before asking questions.
There are some situations where the "in custody" portion of the Miranda requirement is subject to dispute. One example is during a DWI investigation. The traffic stop begins as an "investigatory detention" (where Miranda warnings are not required) and at some point during that investigation, it turns into a custodial arrest (at which point, Miranda warnings are required). An experienced defense lawyer can review the evidence and determine whether statements made during an investigation required a Miranda warning.