When criminal activity occurs within the borders of a single state, state courts tend to have jurisdiction. This means that most crimes are tried at the state level. Whether it is a DUI charge, allegations of robbery or theft, or charges for violent crimes like assault, they tend to be one-time events that happen within the state.
When a crime crosses state lines, however, that can give the federal government jurisdiction. This could escalate things so that a person faces federal charges, all based on the location, rather than just the nature of the crime itself.
Examples of how this could occur
For instance, say that someone is being charged with transporting illegal drugs. If they are just moving them between towns in the same state, they could face state drug charges. But if they drive across state lines—such as if someone buys marijuana in a state where it is legal and then drives into a state where it is not—then they could end up facing federal charges.
Many internet crimes also end up being federal crimes. Say that someone is accused of financial crimes where they used the internet to defraud investors all across the United States. Even though that person may not have physically left the state themselves, their activities affected victims in other states, so they could find themselves facing federal fraud charges.
Your defense options
It is very important to know exactly what types of criminal charges you are facing and whether they will be tried at the state or federal level. As you go through this process, it can help to work with an experienced attorney to consider all of the defense options at your disposal.

