In the short story The Witness for the Prosecution, Mrs Mogson is a woman living at 16 Shaw's Rents in Stepney. She sent a letter to Mr Mayherne, asking to meet him. Mrs Mogson claimed to have proof that Romaine Vole was lying, when she said that Leonard Vole had not been home at 8.20.
She is a middle aged woman with a bent figure and a wheezy voice.