What is defined as a crime when someone has been lawfully arrested?

The correct answer identifies that attempting to flee from a police officer or custodial facility constitutes a crime when someone has been lawfully arrested. This behavior is treated as an offense because it obstructs law enforcement's ability to apprehend and detain individuals securely. Once a person is lawfully arrested, they are in custody, and any attempt to escape can jeopardize the safety of both the individual and law enforcement officers involved.

The other situations mentioned do not necessarily qualify as crimes in the same direct manner. For instance, failure to identify oneself might depend on the specific laws governing that situation and may not always lead to criminal charges. Similarly, refusing to provide assistance to an officer can be viewed in different legal contexts, and while it may be considered uncooperative, it does not have the same legal implications as physically attempting to flee from custody. Walking away from the scene of a crime could fall into ambiguity regarding ongoing investigations, but it lacks the direct element of evading arrest once custody has been established. Hence, the act of fleeing stands out as being clearly defined as a crime upon lawful arrest.