October 2005: Teresa Halbach is murdered
November 2005: A distressed Brendan Dassey — who had lost upwards of 40 pounds — talks with his cousin, Kayla, about Steven Avery.
November 6th, 2005 — Police ask Dassey routine questions as part of their investigation. He denies any involvement, but investigators believe he may be hiding something. Police consider him a potential witness.
January 2005: Kayla confided in school counselors about conversations she had with Brendan.
February 20th, 2005 — Police ask Kayla question as part of their routine investigation into Steven Avery. She offers, unsolicited, that her cousin Brendan Dassey often cried uncontrollably and had lost weight. She implies this may be related to Avery.
February 27th — Police interview Dassey at school without a lawyer present, believing he might have information about Steven Avery’s involvement in the murder of Halbach. Dassey at first denied any involvement, but then he told the police that Avery had asked him not to talk. After more questioning, he admitted he may have seen Teresa’s body, then he admitted that Steven killed Teresa. He denied his own involvement, and provided a written statement of what he knew.
February 28th — Police interview Dassey again, this time at the Two Rivers police department. They sought permission from Dassey’s mother, who provided it. A lawyer was not present because, again, police were interviewing Dassey as a witness, not as a suspect. Again, Dassey implicated Steven Avery in the murder of Halbach. The police, to protect Dassey and his mother from Avery and his family, offer to put them up in a hotel.
Later that night, with Dassey’s mother present, Dassey admitted to police that he helped Steven Avery clean up the crime scene, pouring bleach on the garage floor. He also admitted to having jeans with bleach stains on them, which he provided to the police as evidence.
March 1st — Police asked Dassey’s mother again if they could interview him. She agreed. A lawyer was not present because, again, he was only considered a witness at this time. Here, Dassey confessed not only to being a witness to the crime who helped clean up Avery’s mess, but that he, himself, had been involved in the rape and murder of Halbach. Police were able to corroborate much of Dassey’s confession with physical evidence. The confession was gruesome, and several pages long.
None of this was particularly unusual for a confession. In most cases, a guilty party initially denies wrongdoing, but under multiple rounds of questioning, offers more and more details until he or she admits being a witness, being involved, or outright perpetuating the crime. Confessions, in most cases, come in waves.