Michael Swango was born in Tacoma, Washington, but he grew up in Quincy, Illinois. He was the middle child of Muriel and John Virgil Swango. His father, John, was a career officer in the United States Army who served in the Vietnam War and was even listed in Who's Who in Government from 1972 to 1973. However, after returning from Vietnam, John's life took a dark turn. He became an alcoholic and suffered from depression, which eventually led to his divorce from Muriel. As a result, young Michael saw very little of his father and grew closer to his mother. In high school, Michael was a standout student, becoming the valedictorian of his 1972 class at Quincy Catholic Boys High School. He also played the clarinet in the school band.

After high school, Swango joined the Marine Corps. He completed his recruit training at the Marine Corps Recruit Depot in San Diego and received an honorable discharge in 1980. Although he never saw combat, his time in the Marines instilled in him a strong commitment to physical fitness. Outside of his studies, he was often seen jogging or doing calisthenics around the Quincy University campus. In fact, he would sometimes do pushups as a form of self-punishment when criticized by instructors. Swango graduated summa cum laude from Quincy and was awarded the American Chemical Society Award. Following this, he enrolled in medical school at Southern Illinois University School of Medicine (SIU).

Despite his academic brilliance, Swango's time at SIU was marked by troubling behavior. He was more interested in working as an ambulance attendant than focusing on his studies. His fascination with dying patients raised eyebrows, as many of his assigned patients experienced life-threatening emergencies, with at least five dying. Just a month before graduation, it was discovered that Swango had faked checkups during his OB/GYN rotation. Some of his peers had suspected him of dishonesty since his second year, but this was the first time he was caught. Although he was nearly expelled, one committee member's vote allowed him to stay, as a unanimous decision was required for dismissal. Despite ongoing concerns about his competence, the school allowed him to graduate a year later than his classmates, on the condition that he repeat the OB/GYN rotation and complete additional assignments in other specialties.

In 1983, Michael Swango secured a surgical internship at Ohio State University Medical Center despite a poor evaluation from his previous school. During his time at the hospital, nurses noticed an alarming pattern of healthy patients suddenly dying, and Swango was always the intern on duty when these incidents occurred. One nurse even saw him injecting something into a patient who then became mysteriously ill. When the nurses reported their concerns, hospital administrators dismissed them as paranoid. A superficial investigation cleared Swango, but his work was so sloppy that Ohio State withdrew their residency offer once his internship ended in June 1984.

After leaving Ohio, Swango returned to Quincy and took a job as an emergency medical technician. His behavior raised alarms once more when his coworkers began getting violently ill after consuming food or coffee he had prepared. In October 1984, police arrested Swango after finding arsenic and other poisons in his possession. By August 1985, he was convicted of aggravated battery for poisoning his coworkers and sentenced to five years in prison. This conviction prompted a scathing review of Ohio State's handling of Swango, criticizing the hospital for not involving law enforcement sooner. After his release in 1989, Swango moved to Virginia, where he worked as a counselor and then a laboratory technician. Despite his criminal past, he managed to gain employment using forged documents. During this time, he met and fell in love with Kristin Lynn Kinney, a nurse, and they planned to marry. In 1991, Swango changed his name to Daniel J. Adams and secured a position at Sanford USD Medical Center in South Dakota. 

However, his past caught up with him when the American Medical Association discovered his poisoning conviction. Around the same time, a TV program about Swango aired, leading to his dismissal from Sanford. Kinney later left him due to severe migraines, which mysteriously stopped after their separation.

Swango then found a spot in a psychiatric residency program at Stony Brook University in New York. Once again, patients began dying under his care. Four months into his residency, Kinney died by suicide, and arsenic was found in her body. This tragic event prompted an investigation that revealed Swango's history of poisoning. He was fired from Stony Brook, and the resulting public outcry forced the resignation of key university officials. Swango fled the country, eventually finding work at a hospital in Zimbabwe. His patients there also started dying mysteriously, leading to his suspension and eventual arrest in 1997 upon his return to the United States.

Facing overwhelming evidence of his crimes, Swango pleaded guilty to various charges, including murder, in 2000. He was sentenced to life in prison without parole. Prosecutors believe Swango could be responsible for as many as 60 deaths, making him one of the most prolific serial killers in American history. Swango's preferred method was poisoning, whether it was slipping arsenic into food or overdosing patients on their prescribed medications. He is currently serving his sentence at ADX Florence, a maximum-security prison, where he requested to be held to avoid further attacks from other inmates.