According to 14 CFR Part 107, the responsibility to inspect the small UAS to ensure it is in a safe operating condition rests with the

Why →Under 14 CFR § 107.49(a)(2), the remote PIC must ensure the UAS is in a condition for safe operation before each flight. This duty cannot be delegated to the visual observer or the equipment owner. The remote PIC assumes full legal responsibility for aircraft airworthiness at the time of each flight.

The trap →The owner might be a business or client who hired you. They bear no pre-flight inspection obligation. The visual observer is responsible for watching the airspace, not the aircraft condition.

Field note →Even if you're flying a client's drone, you as the remote PIC are legally responsible for inspecting it before flight. If the drone has obvious damage and the client says "just fly it," you have the authority (and obligation) to ground it.