Nancy Ann D'Onofrio was born on May 13, 1952, in Lincoln Park, Michigan. She was the daughter of Lenore and Eugene D'Onofrio. Growing up, Nancy showed a strong academic ability and was recognized as the valedictorian of her high school class. In 1972, she met a man named Bob Seaman. They got married a year later, in 1973. Bob worked for Ford Motor Company while Nancy took care of their home.

In 1979, Nancy and Bob welcomed their first son, Jeff. They had another son, Greg, in 1981. Nancy spent several years focusing on her family before she began a career as an elementary schoolteacher in 1995.

Nancy's marriage, however, faced serious challenges. Shortly after they married, Nancy experienced her first incident of spousal abuse. She described how her husband, when drunk, tried to push her out of a moving car. Over the years, Nancy claimed that the physical abuse continued sporadically and became more frequent after Bob lost his job at Borg Warner Automotive. Nancy recounted how Bob would shove and push her against walls, causing her bruises.

Nancy's younger son, Greg, stated that he witnessed his father abusing his mother. In contrast, her older son, Jeff, denied any knowledge of such abuse occurring in their home. 

On May 10, 2004, Nancy Seaman and her husband Bob had a serious argument. This fight occurred after Bob returned home from a weekend away. Nancy was planning to move out of their house and into a condo. She claimed that during the argument, Bob became angry and chased her into the garage while holding a kitchen knife. According to the evidence, Nancy took a hatchet from the garage and struck Bob with it at least 20 times.

After the murder, Nancy went to school as a teacher without alerting anyone about the incident. On May 12, 2004, police arrested Nancy after Bob's relative reported him missing. When officers arrived to question her, they discovered Bob's body wrapped in a tarp with duct tape in the back of Nancy's Ford Explorer. They also found the knife used to stab Bob inside the tarp. While Nancy said she acted in self-defense, police believed she had attacked Bob first. They claimed she ambushed him with the hatchet and then dragged his body to the garage.

In the days leading up to the murder, Nancy had made several trips to Home Depot. Surveillance showed her buying a hatchet the day before the murder, a tarp, duct tape, bleach, and cleaning supplies the day after. She was charged with first-degree murder on May 14, 2004, and pleaded not guilty.

Nancy's murder trial began on November 29, 2004. Throughout the trial, she maintained that she killed Bob in self-defense. However, the prosecution argued that Nancy's actions were premeditated. They claimed that she was angry about the upcoming divorce and believed Bob was having an affair. After several days of testimony, Nancy was found guilty of first-degree, premeditated murder. Initially sentenced to life in prison, Nancy's conviction was later reduced to second-degree murder by a judge. However, this reduction was overturned by a higher court, and her sentence was reinstated as first-degree murder.

After exhausting appeals in state court, Nancy sought a new trial in federal court, which was granted when a judge agreed her defense team had not fully argued her case. However, this decision was put on hold, and ultimately, Nancy's request for a new trial was denied by a federal appeals court, which stated that battered spouse syndrome was not a legal defense in Michigan. Nancy is currently serving her sentence at the Women's Huron Valley Correctional Facility.