What is a necessary criterion for an inventory search to be lawful?

For an inventory search to be lawful, it is essential that there is a lawful arrest of the person or a legitimate impoundment of the vehicle. This requirement ensures that the inventory search is conducted within the parameters of the Fourth Amendment, which protects against unreasonable searches and seizures.

When law enforcement officers arrest an individual and subsequently impound their vehicle, they are permitted to conduct an inventory search to account for the contents of the vehicle. This process serves multiple purposes, such as protecting the owner's property while it is in police custody, safeguarding the police from claims of lost or stolen property, and ensuring officer safety by checking for dangerous items.

The other choices do not fulfill the fundamental legal requirement for a lawful inventory search. For instance, allowing personal discretion of the officer could lead to arbitrary actions without proper legal basis. The presence of the arrestee during the search is not necessary for the search itself to be lawful, as inventory searches can be conducted without the arrestee present. Lastly, mandatory approval from a supervisor may be good practice, but it is not a legal requirement for conducting an inventory search, as long as the underlying lawful arrest or vehicle impoundment is valid.