When has sushi gone bad?

Excuse me, could you please clarify when sushi typically goes bad? I understand that it's a perishable food item, but I'm curious about the specific signs or indicators that would suggest it's no longer SAFE to consume. Is it the smell, the texture, or perhaps a combination of both? Additionally, how long does sushi typically last after it's been prepared before it starts to deteriorate? I'd appreciate any insights you have on this matter.