Karen Frank-McCarron was born Karen Frank on December 20, 1968, in Germany to Erna and Walter "Robert" Frank. She grew up in a family that eventually moved to the United States. Karen graduated from Maine South High School in Park Ridge, Illinois. After high school, she attended the University of Illinois at Urbana–Champaign. She later went on to Southern Illinois University School of Medicine in Springfield, Illinois, where she earned a degree in medicine in 1995.

After completing her education, Karen became a pathologist. She worked at Methodist Medical Center and Proctor Hospital in Peoria, Illinois. She also volunteered as a clinical assistant professor at the University of Illinois College of Medicine at Peoria.

Karen met Paul McCarron while they were both students at the University of Illinois. They married and had two daughters. Their first child, Katherine "Katie," was born on July 22, 2002. In 2004, Katie was diagnosed with autism. To help Katie, Paul and Karen made a significant change when Paul moved with Katie to Apex, North Carolina, so she could attend a special education school. They lived there for about 20 months before returning to Illinois.

During her early career, Karen faced personal challenges. While working as a resident doctor in Cleveland, Ohio, she was a patient of a psychologist. Later, in 2005, a psychiatrist began treating her for depression. She was prescribed antidepressants but stopped taking them in early 2006. At her trial later, it was noted that the psychiatrist did not detect any delusional thinking during her treatment.

On the afternoon before Mother's Day, Saturday, May 13, 2006, Karen McCarron killed her daughter, Katherine McCarron, by suffocating her with a plastic bag. After committing the act, she went to a grocery store to purchase ice cream for herself. Later that same day, she confided in family members about what she had done.

In the early morning of May 14, 2006, McCarron attempted to take her own life by cutting herself and consuming a non-fatal dose of Tylenol. She was placed under home confinement while waiting for her trial after posting a $1 million bond.

Her trial began on January 7, 2008. Prosecutors argued that before she suffocated her daughter, McCarron had suggested putting Katherine, who was just three years old and had autism, into an institution and putting her up for adoption. After a week of testimonies, she was found guilty of first-degree murder, obstruction of justice, and concealing a homicidal death on January 17, 2008.

McCarron was sentenced to 36 years in prison, followed by 30 months of supervised release. She was also required to pay a fine of $25,000 to the state of Illinois. Around the same time, her husband Paul filed for divorce, citing mental cruelty. In December 2008, a lawsuit was filed by McCarron’s parents to recover the money they had lent her for her attorney fees during the trial, which they won.

In 2010, McCarron sought to appeal her conviction, but the Illinois appellate court upheld the original ruling. She later filed a petition for a new trial in August 2011, which was denied in November of the same year. Currently, she serves her sentence at Logan Correctional Center in Lincoln, Illinois.