Washington  |  Intellectual Property

My mother wrote and created a children's character with an unusual name, and copyrighted her story. She also had a radio show featuring this character and his friends, produced a record, and planned to publish the first story as well. However, she never totally completed the manuscript, and years later her copyright expired. Shortly after the expiration, a professional person started writing stories using the same name, although nothing else about the stories was similar. I feel that the professional person deliberately stole the name, although I cannot prove it. Now I would like to publish my mother's original stories. But would the professional person who is using the name, be able to accuse ME of stealing it, or is it now considered "public domain" since the original copyright expired? Is there any special paperwork I would need in order to publish? My mother passed away in 1998, and my father (who drew the illustrations) passed in 2008. I want to publish the book as a tribute to them both. I hope someone can help me, please. Thank you for reading.