Ervil LeBaron's attention was also focused on rival polygamous leaders. In April 1975, he ordered the killing of Bob Simons, a polygamist who sought to minister to Native Americans. In 1977, LeBaron ordered the killing of Rulon C. Allred, leader of the Apostolic United Brethren, another Mormon fundamentalist sect. Ervil LeBaron's 13th wife, Rena Chynoweth, carried out the murder with Ervil's stepdaughter, Ramona Marston. Although Rena Chynoweth was tried and acquitted for Allred's murder, she confessed in her memoir, The Blood Covenant (1990). She also described her experiences in LeBaron's group, which she characterized as using mind control and fear to control its followers.
Ervil LeBaron also ordered the murders of members of his own family and those of his supporters. His 10th wife, Vonda White, was convicted and sentenced to life in prison for the murder of Dean Grover Vest, one of LeBaron's henchmen, who had attempted to leave the church. Vonda White is also said to have killed Noemi Zarate Chynoweth, the plural wife of Ervil's father-in-law through his wife, Lorna Chynoweth. Noemi had been critical of Ervil LeBaron's practices and snubbed him at her wedding to Bud Chynoweth. According to witnesses, Thelma Chynoweth (Bud Chynoweth's first wife who was Lorna's mother and Noemi's sister-wife) helped kill Noemi. Ervil LeBaron has also been linked to the death of his own 17-year-old daughter Rebecca, who was pregnant with her second child and hoped to leave the group; it is alleged that his stepson Eddie Marston and brother-in-law Duane Chynoweth strangled her in April 1977.
On June 1, 1979, Ervil LeBaron was apprehended by police in Mexico and extradited to the United States, where he was convicted of having ordered Allred's death. In 1980, he was sentenced to life imprisonment at the Utah State Prison in Draper, Utah, where he died on August 16, 1981. Ervil's brother Verlan (whom Ervil had tried to murder) died in an auto accident in Mexico City two days after Ervil's body was discovered in his cell. In an October 2012 interview with Vice Magazine, Verlan LeBaron's grandson Brent LeBaron stated that at least some in the LeBaron family believe that this may not have been a coincidence.