Which of the following scenarios illustrates lawful consent to search?

The scenario that illustrates lawful consent to search is when a friend allows a police officer to search their vehicle. For consent to be valid, it must be given freely and voluntarily by someone who has the authority to do so. In this case, the friend, as the vehicle owner or authorized user, has the right to allow the officer to conduct the search. This situation aligns with the principles of consent within the context of the Fourth Amendment, which requires that searches be reasonable and based on probable cause, unless there is valid consent.

The other options do not represent lawful consent. An officer demanding to search without explanation raises questions about the voluntariness of the consent and the legality of the search itself. Consent obtained under coercion or duress is invalid, as it contradicts the fundamental requirement that consent must be given freely. Lastly, if an owner is not present to object to the search, it does not inherently grant lawful consent; a third party cannot provide valid consent unless they have the authority to do so, which is not applicable if the owner's presence is necessary for such permission.