Sarah Marie Johnson was born on January 24, 1987, in Idaho. She grew up in the city of Bellevue. Sarah attended Wood River High School in Hailey, where she was a student during her teenage years.

Sarah lived with her parents, Diane and Alan Johnson. They had a family home in Bellevue. Little is known about her life before the events that marked her teenage years. However, it is noted that her parents had strict rules, which affected their relationship with her. As a teenager, Sarah faced issues with her parents regarding her social life. They did not approve of her dating a 19-year-old boy, which caused tension in the household. 

On September 2, 2003, in Bellevue, Idaho, Sarah Marie Johnson killed her parents, Alan Scott Johnson and Diane Johnson, when she was 16 years old. She used a .264-caliber Winchester Model 70 bolt-action rifle. Around 6:20 am, she took the rifle from a guest house on her property. The guest house was not occupied, as the tenant had left for Boise and would not return for about a week.

Sarah first went to her parents' bedroom while they were asleep. She shot her mother, Diane, in the head. After that, she walked into the bathroom where her father, Alan, was taking a shower. She shot him twice in the chest. After the killings, Sarah disposed of evidence, including a bathrobe and a latex glove, in a garbage can outside the house.

During the investigation, DNA evidence was collected from the items found in the trash. This evidence showed DNA from both victims and Sarah. Investigators also found another leather glove belonging to the same pair in her room. The glove had gunshot residue on it.

Sarah was arrested and later tried for the murders. On March 16, 2005, a jury found her guilty. She received two life sentences without the possibility of parole, along with an additional 15 years for the firearm enhancement. The Idaho Supreme Court later upheld her conviction.

In 2012, Sarah's lawyer filed for a new trial, arguing that she had poor legal defense during the original trial. They noted that there was no blood spatter evidence on her and fingerprints on the rifle matched a renter in the guest house. However, this request was denied in October 2014. In 2017, Sarah sought a reduction in her sentence based on recent Supreme Court rulings regarding juvenile sentencing, but her request was denied. She is currently held at the Pocatello Women's Correctional Center.