Wilhelmina Lawson

In the novel Dumb Witness, Wilhelmina “Minnie” Lawson was Emily Arundell's companion for the last year and, according her final will, her sole heiress. After the death of Miss Arundell, Miss Lawson moved to 17 Clanroyden Mansions, Bayswater.

Miss Lawson was described as being a "rather stout, middle-aged lady", with an "eager, rather foolish face, untidy greyish hair and pince-nez".

One night Miss Lawson was awake thinking of a mistake she had done in ordering cold meat and she saw through her looking-glass Theresa Arundell kneeling on the stairs from which Emily would have fallen later on. It appeared that the person she saw planted a nail to make Miss Arundell fall purposefully. The only detail that made Lawson think she saw Theresa Arundell was the brooch in her dressing gown which contained the initials 'T. A.'. However, Poirot later reveals that since she saw the person through a glass, the initials were 'A. T', which pointed to Arabella Tanios.

Wilhelmina was said to love children despite being incapable of managing them.

Wilhelmina was friends with Julia and Isabel Tripp, and was interested in spirituality. She enjoyed attending sittings and using the Planchette with them. According to the Tripp sisters, she was a "thoroughly good woman", and very "unworldly", and she regarded the money from Miss Arundell as a sacred trust. According to them, she was willing to do something for Bella Tanios or the Tanios children, and to make Theresa an allowance.

Wilhelmina was sympathetic to Bella, and helped her when she left her husband, getting her rooms at the Wellington Hotel.

It is later revealed that Wilhelmina had seen Miss Arundell's will, and knew that Miss Arundell had left all her money to her. When Miss Arundell asked for the will, Wilhelmina told her that it was with Mr Purvis, as she felt sure that Miss Arundell was going to destroy the will. She felt guilty about this, and when Bella came to her after leaving her husband, she told Bella that she could have half of the money, believing that that would make her feel better.

At the end of the novel, it is revealed that Wilhelmina had to be "restrained forcibly from denuding herself of every penny". A settlement is drawn up whereby the money is shared between Wilhelmina, Charles Arundell, Theresa Arundell, and the Tanios children.

It is also revealed at the end of the novel that Wilhelmina gave Bob to Poirot.

Agatha Christie's Poirot
The part of Minnie Lawson was played by Norma West in the 2000 ITV TV adaptation which came under the form of an episode for the series Agatha Christie's Poirot.

Témoin Muet
In Témoin muet, the France Televisions and Escazal Films adaptation of the novel, the parallel character is Geneviève Ranson who similarly was the sole beneficiary of Émilie Longuet's will. Here she was actually married to a man named Hubert Dambreuse who was killed by Emilie. This may have been a reason for Emilie to change her will in favour of her companion and disinherit her relatives.