When does a Developer become accountable for an item in the sprint Backlog?

A Developer becomes accountable for an item in the Sprint Backlog never as Developers on the Scrum Team share accountability for items in the Sprint Backlog, as stated in the Scrum Guide: “The Developers can select whatever items they want as long as they feel they can complete the work by the end of the Sprint. The Scrum Team is responsible for all estimates. The Product Owner may influence the Developers by helping them understand and select trade-offs, but the people who will perform the work make the final estimate.”