Arthur Adams: Miss Gilchrist’s downstairs neighbor.
Dr. John Adams: The first doctor at the murder scene; not related to Arthur Adams.
Craigie Aitchison: Slater’s barrister in the 1928 rehearing of his case.
Andrée Junio Antoine (“Madame Junio”): Slater’s mistress; allegedly a prostitute.
Annie Armour: Glasgow subway clerk; witness for the prosecution at Slater’s trial.
Mary Barrowman: Teenage delivery girl who claimed to have witnessed the murderer’s flight along West Princes Street.
Dr. Joseph Bell: Conan Doyle’s medical-school teacher, master diagnostician, and the model for Sherlock Holmes.
Margaret Birrell: Miss Gilchrist’s niece.
Hugh Cameron: Glasgow bookmaker and friend of Slater’s; he directed police to the shop where Slater had pawned a diamond crescent brooch.
Francis Charteris: Eminent Glasgow physician and nephew of Miss Gilchrist.
David Cook: Glasgow lawyer; friend and supporter of Detective Lieutenant Trench.
William Miller Douglas: Superintendent, Glasgow police.
George Edalji: Anglo-Indian lawyer whose wrongful conviction for animal maiming Conan Doyle helped overturn in 1907 in a case that prefigured Slater’s.
Maggie Galbraith Ferguson: Miss Gilchrist’s former maid, who, with her daughter, Marion Gilchrist Ferguson, was the chief beneficiary of Miss Gilchrist’s new will.
Charles Fox: Counsel for the British Crown at Slater’s extradition hearing in New York.
Marion Gilchrist: The victim.
Sir John Gilmour: Secretary of State for Scotland, 1924–29.
John Glaister: Forensic-medicine expert; witness for the prosecution at Slater’s trial.
William A. Goodhart: Slater’s primary defense lawyer at his New York extradition hearing.
William Gordon: Slater’s fellow convict; on his release in 1925, he smuggled Slater’s urgent message to Conan Doyle.
Agnes Guthrie: Helen Lambie’s former employer.
The Hon. Lord Charles John Guthrie: The judge at Slater’s trial.
James Hart: Procurator fiscal for Lanarkshire, instrumental in Slater’s wrongful conviction.
Helen (Nellie) Lambie (later Gillon): Miss Gilchrist’s maid.
Adolf Leschziner: father of Slater (born Oskar Josef Leschziner).
Euphemia (Phemie) Leschziner: Slater’s sister.
Georg Leschziner: Slater’s brother.
Pauline (or Paula) Leschziner: Slater’s mother.
Rowena Adams Liddell: Sister of Arthur Adams.
Duncan MacBrayne: Glasgow greengrocer who could have alibied Slater; he was not called at trial.
Colin MacCallum: Glasgow bootmaker and employer of Mary Barrowman.
Alexander Logan McClure: Slater’s barrister; argued his defense at trial.
Ramsay MacDonald: British Labour Party leader; British prime minister, 1924, 1929–31, 1931–35.
Allan McLean: Glasgow bicycle dealer; informed the police of Slater’s pawn ticket.
Erna Meyer: Daughter of Slater’s sister Phemie.
James Gardner Millar: Lawyer and sheriff of Lanarkshire; presided at the 1914 secret inquiry.
John Ord: Senior superintendent, Criminal Investigation Department, Glasgow police.
John Orr: Chief superintendent, Glasgow police.
Ernest Clephan Palmer (“The Pilgrim”): British journalist; author of a 1927 newspaper exposé on the Slater case.
William Park: Glasgow journalist, and author of the 1927 book The Truth About Oscar Slater, edited and published by Conan Doyle.
Rev. Eleazar P. Phillips: Leader of the Garnethill Hebrew Congregation; a Glasgow Jewish clergyman who was Slater’s longtime supporter.
John W. M. Pinckley: United States deputy marshal at Slater’s extradition hearing.
John Pyper: Detective inspector, Glasgow police; instrumental in Slater’s extradition proceedings in New York.
William Roughead: Scottish lawyer, criminologist, and journalist; editor of Trial of Oscar Slater, published in four editions between 1910 and 1950.
Catherine Schmalz: Slater’s maid.
Alexander Shaughnessy: Slater’s second Glasgow solicitor; succeeded Ewing Speirs.
John A. Shields: United States commissioner for the Southern District of New York; presided at Slater’s extradition hearing.
John Sinclair: Secretary of State for Scotland, 1905–12.
Ewing Speirs: Slater’s first Glasgow solicitor.
Amalie (Malchen) Leschziner Tau: Slater’s sister.
Käthe (Kätel) Tau: Daughter of Slater’s sister Malchen.
John Thomson Trench: Detective lieutenant, Glasgow police; his support of Slater in the 1914 inquiry resulted in his own ruin.
Alexander Ure: Lord Advocate; chief prosecutor at Slater’s trial. Later elevated to the peerage as Baron Strathclyde.
William Warnock: Chief criminal officer of the Glasgow sheriff court; instrumental in Slater’s extradition proceedings in New York.
Thomas McKinnon Wood: Secretary for Scotland, 1912–16.