Jurisdiction is… interesting. If you watch cop shows or legal dramas, it’s a term you’ve heard thrown around, yet few people have a firm handle on what it means. Today I’m going to fix that.

At its most basic level, jurisdiction simply refers to the legal authority to handle a particular case. Law enforcement agencies have particular jurisdictions, as do courts. Technically, jurisdiction refers to a particular subject matter—that is, whether an agency has power to deal with a particular type of case. A small claims court does not have jurisdiction to hear a murder case. Your local police department does not have jurisdiction to make arrests for federal immigration offenses.

In practice, however, we often use jurisdiction in a geographic sense as well. The LA County Sheriff’s Department has jurisdiction in LA County—and not, say, in Kern County.

Jurisdiction is a complicated issue in the US because our legal system is fragmented. While most countries have a single (federal) court system and a single (federal) law enforcement agency, we don’t. We have state and federal courts, some of them with quite specific areas of authority (such as military cases or bankruptcy cases). And we have many thousands of police agencies at local, state, and federal levels.

Jurisdictions can overlap. Imagine I kidnap someone in Wyoming and drag him to my hometown, only to be caught on the nearby university campus. In that case, dozens of law enforcement agencies might be involved, including the FBI (a federal agency) and many state and local police departments. Just from my own area, my city police, the Highway Patrol, and the campus police might be there (the latter two are both state agencies). It can be confusing! And while agencies very frequently cooperate with one another, sometimes friction or rivalry may exist.

The takeaway for you as an author? If a police department or court is dealing with a case in your book, make sure they have proper jurisdiction. That may require research to determine who handles what, but you definitely don’t want to get it wrong.