Complex sentence: Hardy is initially doubtful, thinking that Dunbar may be trying to use the knowledge of Hardy's role as a DEA agent to sell a story, however Dunbar produces a needle containing the steroid cocktail that he had hidden on his body as proof of his story.
Split into simpler sentences: Hardy is initially doubtful, thinking that Dunbar may be trying to use the knowledge of Hardy's role as a DEA agent to sell a story. However Dunbar produces a needle containing the steroid cocktail that he had hidden on his body as proof of his story.