Which of the following may cause AED pads to not stick to a victim's chest?

A wet chest surface can significantly hinder the adhesion of AED pads to a victim's skin. When the skin is wet, the moisture acts as a barrier, preventing the pads from establishing the necessary contact to allow for effective delivery of shocks if needed. For optimal function, the skin must be dry and free from any liquid that could interfere with the electrical conduction between the pads and the victim's body.

While other factors like wearing a shirt, expired pads, or a malfunctioning AED can affect the overall efficacy of the defibrillator's operation, they do not directly impact the sticking capability of the pads to the skin as profoundly as a wet surface does. Removing moisture from the chest area is essential for the AED to function correctly, elevating the importance of ensuring that the chest is dry before pad application.