When Anna was arrested and tried for the murder, he claimed that all the Sinclair children bought enough to kill their father, and couldn't provide any evidence that she had definitely committed the crime.
^Pierre, "Murder Mystery", RuneScape. "Honestly? I think it was Carol. I saw her in a huge argument with Lord Sinclair in the library the other day. It was something to do with stolen books. She definitely seemed upset enough to have done it afterwards."