Complex sentence: She was once arrested for drug smuggling, as detailed in her autobiography, for one "joint," which she brought in her luggage for a friend without knowing that possession of this small amount of marijuana was a serious offence.
Split into simpler sentences: She was once arrested for drug smuggling, as detailed in her autobiography. In fact, it was only one "joint," which she brought in her luggage for a friend without knowing that possession of this small amount of marijuana was a serious offence.