Marybeth Roe Tinning was born on September 11, 1942, in Duanesburg, New York. Her parents were Ruth and Alton Lewis Roe. During her childhood, her father was often away serving in World War II while her mother worked to support the family. As a result, Marybeth was sometimes cared for by various relatives. One elderly relative even told her she was an unwanted child. This sentiment impacted her, and she later expressed feelings of not being the preferred child compared to her younger brother.

After the war, Marybeth's father found work as a press operator at a General Electric factory, which was the largest employer in their area. As an adult, Marybeth made allegations of abuse toward her father. In a police interview in 1986, she claimed he had physically punished her and locked her in a closet. However, during her court testimonies, she downplayed these incidents, saying her father did not intend to harm her and that his actions stemmed from his arthritis.

Marybeth attended Duanesburg High School, where she was an average student. She graduated in 1961. After high school, she worked various low-paying, unskilled jobs. Eventually, she became a nursing assistant at Ellis Hospital in Schenectady, which was located about ten miles from her hometown.

In 1963, Marybeth went on a blind date with Joseph Tinning. The couple married two years later in 1965. They welcomed their first child, Barbara, in May 1967 and their second child, Joseph Jr., in January 1970. In October 1971, Marybeth's father passed away from a heart attack.

In 1974, Joseph was hospitalized for severe barbiturate poisoning. This incident occurred during a troubling time in their marriage. During this period, Marybeth admitted to putting borrowed pills into Joseph's grape juice, though he chose not to press charges against her.

On December 26, 1971, Marybeth Tinning gave birth to her third child, Jennifer. Jennifer suffered from serious health issues and died on January 3, 1972. Shortly after, Marybeth took her two-year-old son, Joseph Jr., to the emergency room, claiming he had experienced a seizure. Joseph was released after doctors found nothing wrong, but he died a few hours later on January 20. His death was attributed to cardiac arrest.

On March 1, 1973, Marybeth rushed her daughter, Barbara, to the hospital after she had convulsions. Barbara died the next day, and her death was ruled as Reye syndrome. Later that year, Marybeth gave birth to her son, Timothy, who died a few days after his birth, with doctors attributing his death to Sudden Infant Death Syndrome, or SIDS.

Marybeth's fifth child, Nathan, was born in March 1975, but he died in the fall while Marybeth was driving with him. She later adopted a newborn named Michael in August 1978. On October 29, Marybeth gave birth to Mary Frances. She took Mary Frances to the emergency room in January 1979, claiming she had a seizure. Doctors were able to revive her, but she suffered irreversible brain damage and died two days later after life support was removed.

In March 1980, Jonathan, the Tinnings' eighth child, was born, and he died in March 1980 after being on life support for four weeks. Then, in February 1981, her adopted son, Michael, suffered a concussion from falling down the stairs. Marybeth took him to the doctor, but he was already dead upon arrival.

Tami Lynne, Marybeth's ninth child, was born on August 22, 1985. On December 20, she died from asphyxia. Soon after Tami Lynne's death, officials began to examine the earlier child deaths. Autopsies on the other eight children did not show clear signs of abuse at first.

Marybeth and her husband, Joseph, were called into the police station after Tami Lynne's death. During questioning, Marybeth confessed to murdering Tami Lynne, along with Timothy and Nathan. She later claimed that her confession was coerced.

An autopsy by Dr. Michael M. Baden indicated that Tami Lynne's death was caused by smothering. Authorities began to investigate the deaths of the other children more closely after this finding.

Marybeth was arrested and charged with Tami Lynne's murder. Her trial started in June 1987. Expert testimony concluded that Tami Lynne was smothered. After a lengthy trial, the jury found Marybeth guilty of second-degree murder and sentenced her to 20 years to life in prison.

Marybeth appealed the conviction, claiming her confession was not given willingly. However, her appeal was denied. She made several attempts to gain parole over the years but was denied multiple times due to a lack of remorse. On August 21, 2018, after serving 31 years, Marybeth was released on parole under strict conditions.