What writing characteristics determines that a biography is an autobiography?

A biography is a life story. It can be written by anyone. An autobiography is a life story written by the subject themselves. In today's society, ghost writers are often hired to write an "autobiography" for someone (such as a celebrity) who then published it under their own name as if they had written it themselves. Charles Barkley famously contradicted much of the information in his autobiography, and then revealed he never read his "autobiography".