A French prostitute with a reputation of being "unchaste", Tapper previously lived in Fulda, Minnesota and later Heron Lake,[2] before moving to Denver as the mistress of Richard Demady.
Both were part of a secret French order called the Macquereaux, or Les Cavaliers d'Amour, in which Tapper played the role of a sex servant.
[9] One of the prime suspects in the case was Frenchman Richard Demady, who lived with Lena Tapper and was also part of the Macquereaux.
[11] The announcement caused great excitement in the country, with the District Attorney's office claiming they could prove that he strangled at the very least Tapper.
[12] A total of 45 witnesses were brought in to testify, among them Laura Johnson, a woman with whom Demady was intimate, who was supposed to give a sensational testimony against him.
The prosecuting attorney claimed to have conclusive proof, including a check written by Demady, which was used to bribe a judge into releasing him.
A married French Canadian roustabout who lived in a small house near Market Street, Roch was arrested by authorities when it was discovered he matched the description of a man running away from the Oyama crime scene shortly after the murder.
[18] On November 18, 1894, an Italian man known only as H. Meller (or Moeller) entered the house of Marie Vendres, and after a quarrel, he began strangling the woman.
[11][19] An approximately 40-year-old French carpenter with abnormally large hands, Monchereaux first came to the attention of the police after his former friend and fellow Frenchman, Alphonse Lemaire, drunkenly told a story of how he committed the crimes.
Lemaire had entered the saloon of a man named Frank Klepfel in a half-drunken state, sitting down at a table and watching an ongoing billiard game, without moving much.
Tony Sanders, the lover of the deceased Contassoit who was present at the time and searching for any possible clues, began paying attention to the new arrival.
Klepfel and half the men in the saloon also began paying attention, giving Lemaire even more alcohol.
[20] The pair initially met while serving time in San Quentin, California, with Monchereaux arriving in Denver in 1893 and Lemaire three months before the murders.
Not only that, but he had also planned to kill another woman by the name of Xavier, using a long plank which he would place in the small back yard to get across.
[21] Although police considered that neither of the prisoners were responsible and were simply pawns of the Macquereaux,[22] for a short while, they began suspecting that it was actually Lemaire who might be the strangler.
[23] According to Monchereaux's account, the vagabond sailor Lemaire arrived in Denver from Salt Lake City under his real name, Charles Guichard.
[24] His story was partially corroborated by J. W. Williams, a black hod carrier, who had caught up to the men while walking on Market Street and eavesdropped on their conversation.