Michael Ramos sued the Cobb County Sheriff in his official capacity after injuring his knee while performing detention-center landscaping work without what he said was proper footwear. The issue was whether Ramos had carried his burden to show a waiver of sovereign immunity, particularly through alleged liability insurance. The Court of Appeals of Georgia affirmed dismissal for lack of subject-matter jurisdiction. It held that the liability-insurance waiver in OCGA § 33-24-51 applies to negligent use of a covered motor vehicle, not this landscaping injury; Ramos identified no other statute or policy details establishing a waiver. Sovereign immunity is a jurisdictional bar, and the plaintiff bears the burden of pleading and proving a specific waiver. Ramos could not shift that burden by invoking failure-to-state-a-claim standards or asking for discovery for the first time on appeal.