Timothy Baily Hennis was born on February 24, 1958, in Rochester, Minnesota. He grew up in this city and graduated from Mayo High School in 1976. His father, Robert Hennis, worked as a manager at IBM Rochester during Timothy's childhood. After finishing high school, Hennis found work in Rochester before deciding to join the United States Army in 1980.

In the Army, Hennis served in various capacities, including as a parachute rigger at Fort Bragg, North Carolina. During this time, he married a woman named Angela. Together, they had a daughter in 1985. Hennis was focused on his family and career while building a life in the military. By May 1985, Hennis was established at Fort Bragg, working as a parachute rigger. 

On May 7, 1985, Timothy Hennis responded to an advertisement placed by Kathryn Eastburn to rehome her family's dog. He took the dog home after a short visit. A few days later, on May 11, after failing to reach her by phone, Gary Eastburn, Kathryn's husband, became worried. On May 12, a neighbor and a police officer checked on the Eastburn home. They found the bodies of Kathryn and her two daughters, Kara and Erin. Kathryn had been raped and stabbed multiple times. Kara and Erin also suffered serious injuries but Jana, the youngest child, survived the attack.

The investigation began with Detectives Robert Bittle and Jack Watts. They discovered evidence at the crime scene, including fingerprints and hair. A witness, janitor Patrick Cone, reported seeing a man matching Hennis's description leaving the Eastburn home on the morning of May 10 with a garbage bag. Hennis was interrogated on May 15, admitting to taking the dog but denying further contact with Kathryn. Due to his resemblance to a composite sketch based on Cone's description, Hennis was identified as a suspect. Cone later picked Hennis out of a photo lineup, leading to Hennis's arrest.

During the investigation, authorities found that Kathryn’s stolen ATM card had been used after her death. Hennis had a prior criminal record for writing bad checks. His alibi was challenged by earlier acquaintances, and witnesses claimed to have seen him acting suspiciously. After being found guilty during his first trial in 1986, Hennis was sentenced to death. A letter from an anonymous person claiming responsibility for the murders arrived after his sentencing.

In 1989, Hennis’s conviction was overturned based on claims that graphic evidence unduly influenced the jury. He was acquitted in a subsequent retrial. Following his release, Hennis re-enlisted in the Army and served multiple tours, eventually reaching the rank of master sergeant.

In 2006, new DNA evidence linked Hennis to the Eastburn murders. He was recalled to military service and tried again in 2010 under military court-martial. After three weeks of trial, Hennis was found guilty and sentenced to death again. He remains imprisoned at the United States Disciplinary Barracks at Fort Leavenworth, Kansas. Hennis has since filed several appeals regarding his conviction and the jurisdiction under which he was tried, but his appeals have largely been unsuccessful.