Ellis was arrested as a suspect on September 7, 2009, and convicted for the seven murders in February 2011, receiving seven consecutive life sentences without the chance of parole.

Beginning in early childhood, Ellis showed signs of antisocial behavior, acting impulsively and aggressively towards his peers, frequently assaulting classmates and neighboring children.

[2] After finishing the 8th grade, he dropped out of school in 1974 due to poor academic performance and chronic absenteeism, turning towards a life of crime.

[3] A year later, in May 1980, while trying to become a pimp, he got into a fight with local hustlers and prostitutes, for which he was arrested and charged with extortion but later released due to lack of evidence.

When he was released on January 9, 1990, Ellis joined a drug trafficking ring, "The Brothers of the Struggle," who frequently engaged in rivalry with other gangs based in Milwaukee.

[3] In December 1992, Ellis was arrested for leaving the premises without permission but was freed from any punishment after he informed the authorities about the rampant corruption.

[3] In May 2009, while reexamining the cold case murders of seven prostitutes between the ages of 19 and 41, the Milwaukee police learned via a DNA analysis that all of the killings were committed by a single perpetrator.

[4] A statewide investigation eventually discovered that the Justice Department was missing saliva and blood samples from inmate Walter E. Ellis, which were apparently lost on the way to the forensic labs.

A toothbrush containing traces of his saliva was confiscated and examined, and within a few days, Ellis' DNA was matched to the murders of nine women in a three-mile area of northern Milwaukee, spanning from 1986 to 2007.

[8] Aside from her, he was also a suspect in the murder of 16-year-old Jessica Payne on August 30, 1995; unlike the other victims, she had died from blood loss due to a slash to her throat; this discrepancy caused the prosecutor to not press charges against Ellis, rationalizing that he might have only raped her.

In February of that year, however, after consulting with his lawyer, Ellis accepted a plea agreement by the prosecutor's office, admitting his guilt and petitioning for a sentence without trial.