Complex sentence: Gareth Sewell Penn (born 1941 in Carmel, California) is an American true crime author and amateur detective known for being among the first non-journalists to write about the famous Zodiac Killer case.
Split into simpler sentences: Gareth Sewell Penn (born 1941 in Carmel, California) is an American true crime author and amateur detective. Penn was among the first non-journalists to write about the famous Zodiac Killer case.