Stacey Ann Lannert was born on May 28, 1972, in St. Louis, Missouri. She was the daughter of Deb Underwood and Thomas Lannert. Stacey had a close bond with her father, who made her feel special during her early years. However, things took a dark turn as her father began drinking heavily. When Stacey was eight years old, he started sexually abusing her, and the abuse escalated to rape when she was nine.

Stacey's parents divorced when she was young. After the divorce, she tried to tell her mother and a babysitter about the abuse. However, she struggled to find the right words to explain what was happening. Her father had also threatened her, making it difficult for her to speak up. Stacey's sister, Christy, who was two years younger, faced physical abuse from their father starting in first grade. He became particularly violent when he had been drinking.

In the months leading up to a significant event in her life, Stacey moved to Guam to live with her mother. This relocation happened six months before a tragic incident. During this time, Christy expressed a strong desire for Stacey to return home. Stacey attempted to convince their father to let Christy come live with them, but he refused her request.

At the age of 18, Stacey Ann Lannert shot her father, Tom Lannert, twice while he was sleeping on a sofa in their home in St. John, Missouri. This incident occurred in the early morning hours of July 4, 1990. Stacey testified that she had suffered abuse at his hands since she was eight years old. Fearing for her sister's safety, she decided to end his life.

After entering the house through a basement window with her sister, Stacey saw a rifle and made her decision. She found her father asleep on the sofa and shot him. The first shot caused him to wake, and out of fear, she shot him again. Following the shooting, she consulted a friend for advice on what to do next. With their help, she attempted to dispose of the rifle. Initially, she called the police, pretending to have found him dead, but later confessed to Lt. Tom Schulte.

Stacey was charged with first-degree murder. Her defense attorney tried to argue that she was insane or had a mental defect. They aimed to use the "battered spouse syndrome" as part of her defense, but the court limited this defense before the trial. The prosecution claimed she killed her father for financial reasons, while Lannert insisted that she reported his abuses to various adults in her life without any action taken.

During the trial, Stacey’s claims of self-defense were rejected by the judge, who stated she was not in immediate danger when she shot her father. On December 15, 1990, the jury found her guilty and she was sentenced to life in prison without the possibility of parole.

Her sister, Christy, was also tried and convicted for conspiracy to commit murder and served two and a half years in prison. Over time, some jurors expressed regret that crucial evidence about Stacey’s history of abuse was not presented during her trial.

After several years of legal battles and appeals, the court upheld the original judgment. In 2009, Missouri Governor Matt Blunt commuted her sentence, acknowledging the abuse she suffered. Stacey was released shortly after and has since been involved in various community service projects. She also started a non-profit organization aimed at helping other abuse survivors and has shared her story through various media outlets, including a memoir.