She is best known for her role in organizing The Longest Walk, and for serving as a key witness[10] in the trials of AIM members Arlo Looking Cloud, Richard Marshall, and John Graham who were ultimately convicted in the murder of Anna Mae Aquash.
[14] Dennis Banks, co-founder of the American Indian Movement and one of its leaders, 34 at the time, started having a sexual affair with Nichols when she was 15-years-old, and had their first child together when she was 17.
[16] Shortly after the conviction of Arlo Looking Cloud[17] on 8 February 2004 for the first-degree murder of Anna Mae Aquash,[18] Nichols would marry Robert Ecoffey,[13] who served as the lead investigator into Aquash's murder and now Bureau of Indian Affairs superintendent for the Pine Ridge Indian Reservation in September 2004.
[4] The Longest Walk came to an end on 15 July 1978 when approximately 2,000 people entered the United States nation's capital, traveled to Meridian Hill Park and stopped at the Washington Monument.
[25] The Longest Walk was a resounding success, as the demonstration brought international attention and outrage against the federal paternalism the nation's Native Americans were facing, and resulted in the bills being defeated.
[27] However, following the murder of activist and friend Anna Mae Aquash, she began to reconsider her steadfast alliance with the group.
[28] Nichols contacted the FBI, agreed to cooperate in Aquash's murder investigation[21] and later wore a wire to record conversations with Arlo Looking Cloud, Dennis Banks and others.
Although Banks refused to discuss Aquash, he directed the conversation to Robinson, saying that he had been shot by another AIM officer and bled to death because the group was under siege and had no way to treat him adequately.
[35][37] Fritz Arlo Looking Cloud, an Oglala Sioux[38] and adopted brother of former American Indian Movement member Richard Two Elk,[39] was arrested 27 March 2003 in Denver, Colorado on a warrant issued by federal authorities in South Dakota, in which Looking Cloud and another man were accused of shooting Pictou-Aquash during a kidnapping in December 1975 near Wanblee, South Dakota.
[44] Nichols-Ecoffey also discussed rumors that Aquash was an informant, which were known to or held as suspicions by nearly twenty members of the American Indian Movement.
[44] In February 2004, a federal jury composed of seven women and five men deliberated for approximately seven hours before convicting Arlo Looking Cloud in the 1975 execution-style slaying of Anna Mae Pictou Aquash.
[48][49] John Graham, of Southern Tutchone ethnicity,[50] a native of the Yukon and father of eight, was living in Vancouver when he was charged in the United States on 30 March 2003, with the 1975 first-degree murder/pre-meditated murder of Anna Mae Aquash.
[54] On 2 December 2010, South Dakota Judge John Delaney forbade any mention to jurors of a finding in the first autopsy report for Aquash suggesting that she may have had sex shortly before her death, a finding that prosecutors believed originated from Graham allegedly raping Aquash during her kidnapping.
"[55] Nichols-Ecoffey was forbidden by Circuit Court Judge John Delaney from telling jurors exactly what she alleged group member Leonard Peltier told her six months before Pictou-Aquash was killed.
The judge deemed it hearsay, but under questioning from prosecutors, she was allowed to say that Peltier made an "incriminating" statement.
[56] Nichols-Ecoffey has been both praised and condemned for cooperating with the federal government and testifying against John Graham, Richard Marshall, and Arlo Looking Cloud.
[57] Barry Bachrach, one of Leonard Peltier's defense lawyers, claimed Nichols had received money from the FBI in exchange for her testimony.
[59] During United States v. Looking Cloud, Nichols acknowledged receipt of $42,000 from the FBI in connection with her cooperation on the case, money she explained was compensation for the expenses she incurred while traveling to collect evidence by wearing a wire while visiting her ex-husband, Dennis Banks.