Arguably Zellner's most infamous client was Larry Eyler, a Death Row prisoner convicted of murder. He died from complications due to AIDS while incarcerated before an execution date was set, but he'd privately confessed to Zellner 21 other unsolved murders he'd committed before he died. While he was alive, she was bound by attorney-client privilege to protect her client, but two days after his death, she called a press conference and revealed the names and details of his victims.

"It's been really hard on me knowing all this stuff," she told the Chicago Tribune in 1994. "I had these victims' families pleading with me during his life to tell them what happened. I couldn't do it. That's a terrible situation to be in. Your heart tells you to do one thing, and your professional obligations dictate that you do something else. My heart always was on the side of the victims."

In 2002, Zellner successfully vacated the convictions of four men held responsible for the 1986 rape and murder of medical student Lori Roscetti, according to the Chicago Tribune. After DNA tests of hair found on the victim didn't match any of the men convicted of her murder, Zellner told the paper, "It is the last straw. There is no case left. Hopefully, they will do the right thing and release them all on the next court date."

In 2004, Wilmington, Illinois resident Kevin Fox was charged with the sexual assault and brutal murder of his six-year-old daughter Riley, according to Chicago Magazine. Almost immediately, he came forward saying his confession was coerced by the Will County Sheriff's Office, but he spent eight months in jail awaiting trial before being exonerated by DNA evidence discovered by Zellner. She also filed a civil rights case against the Sheriff's Office on behalf of the Fox family and won them a $15.5 million settlement, according to her website.

In 2013, Mario Casciaro was sentenced to 26 years in prison for the murder of his teenage coworker Brian Carrick after a third coworker, "facing a lengthy sentence in an unrelated drug case, agreed to testify against Casciaro in exchange for immunity in Carrick's death," according to the Chicago Tribune. He later recanted his testimony, saying it was fed to him by the prosecution, and Zellner, yet again, discovered more DNA evidence exonerating Casciaro that wasn't brought forth in the initial trial. In 2017, she told the Tribune that she was seeking "millions" of dollars in damages for her plaintiff.

In 2005, Jerry Hobbes called the police to report that he'd discovered the bodies of his 8-year-old daughter and her 9-year-old friend, according to the Chicago Tribune. He wound up being charged with their murders by Lake County prosecutors and spent more than five years in prison after signing a false confession. Although it was his public defender Keith Grant who found new DNA evidence pointing to another suspect (leading the prosecution conclude that they couldn't prove beyond a reasonable doubt Hobbes' involvement in the killings), Zellner represented Hobbes in his civil rights lawsuit against the police. She eventually settled the case for $7.75 million, according to The National Trial Lawyers organization, the largest civil rights settlement in Lake County.

Kathleen Zellner's claim to fame is having righted more wrongful convictions than any other private attorney, and although she's still chipping away at Steven Avery's case, Making a Murder Part 2 unveils some convincing evidence in his favor.