Chad Daybell originally told police that Tammy Daybell had died in her sleep after she went to bed with a cough.

Source: https://www.deseret.com/2023/4/10/23677433/tammy-daybell-cause-of-death-lori-vallow-trial-opening-arguments

It was also discovered that Lori Daybell conspired with her husband, Chad Daybell, to kill the latter’s first wife, Tammy Daybell, in the same year.

Source: http://davidsonian.com/2023/08/04/after-murdering-her-children-in-2019-lori-daybell-smirks-in-her-prison-booking-photo-despite-life-imprisonment-without-parole-on-monday/

Ms Vallow is also charged with conspiracy to murder Mr Daybell’s first wife Tammy Daybell, who died suddenly in her sleep in October 2019.

Source: https://www.independent.co.uk/news/world/americas/crime/lori-vallow-daybell-trial-updates-b2317152.html

On the first day of Lori Daybell’s trial, it was revealed publicly that Tammy Daybell died from asphyxiation.

Source: https://www.eastidahonews.com/2023/04/testimony-turns-to-tammy-daybells-death-in-murder-trial-as-jurors-hear-from-her-sister/