What happens if someone commits a crime in one state and runs to another?

 Extradition is where one state transfers a defendant to another state to face trial.   The United States Constitution (Article IV Section 2) requires states to extradite persons accused of crime.  There is also federal law requiring extradition.  

Each state has its own rules governing extradition but generally speaking, when one state demands that a second state extradite a defendant, the defendant must be extradited.