‘A Killer Story’: The Harrowing Backstory of HBO’s New Docuseries

The new HBO docuseries A Killer Story details not just a crime, its victims, and the convicted perpetrator, as many true-crime productions do. It also profiles an obsessive citizen sleuth and the journalist she needled to look into the case. The result is a documentary filmed over six years of a two-plus-decade legal saga, with many questions still unanswered. Here’s what we know about the docuseries and its key players…

A Killer Story revolves around the murders of Mike Sisco and Karen Harkness.

Mike Sisco, 47, and Karen Harkness, 53, were shot to death on July 7, 2002, at Harkness’ home in Topeka, Kansas, according to CBS News. They were each shot at least five times with bullets sourced from an Israeli weapons manufacturer and typically fired from a military-style weapon, per Vanity Fair. Investigators found the couple’s cash and jewelry still in their house but never recovered the murder weapon, DNA, or fingerprints.

Dana Chandler, Sisco’s ex-wife, soon came under police suspicion after relatives of Harkness and Sisco told investigators that Chandler and Sisco had a bitter divorce and custody battle and that she had harassed him with visits and frequent phone calls. But Chandler, who continues to maintain her innocence, wasn’t charged with the crime at the time.

And so the investigation into Sisco and Harkness’ murders had gone cold by the time CBS News’ 48 Hours started covering the case in 2008. But in 2011, Chad Taylor, then the new district attorney of Shawnee County, pushed the case again forward. Chandler was arrested that year, tried and convicted of two counts of first-degree murder in 2012, and sentenced to life in prison.

Dana Chandler, Sisco’s ex-wife, is serving consecutive life terms for the crimes.

Then came one twist of many: In 2018, the Kansas Supreme Court overturned Chandler’s case, determining that Taylor and prosecutor Jacqie Spradling falsely made the jury believe Chandler had violated a protection order that didn’t exist, according to The Topeka Capital-Journal. Mike Kagay, Taylor’s successor, chose to proceed with another trial, which started in 2022. That trial, however, ended with a hung jury.

A third trial started in 2025, and on the day of opening statements, Chandler dismissed her attorneys, opting to represent herself. Chandler testified for about 20 hours, saying she never owned a 9mm gun and that no one could place her in the state of Kansas at the time of the killing. She also questioned her two children, who believed her to be guilty of killing their father. The prosecution, meanwhile, argued that Chandler had displayed obsessive behavior and had killed the victims because she had lost control of her ex-husband. After deliberating for four hours, the jury in that trial found Chandler guilty, and a judge sentenced her to two consecutive life sentences.

Chandler has been appealing that conviction, though her 14th attorney asked to be removed from the case this March, as the Capital-Journal reported at the time.

True-crime buff Eileen Umbehr and her husband intervened on Chandler’s behalf.

As the documentarians behind A Killer Story know, it’s impossible to chronicle Chandler’s legal saga without mentioning Eileen Umbehr’s involvement. Umbehr is a true-crime TV fan who, alongside husband Keen, got clued into the case through 48 Hours’ coverage, according to Vanity Fair. During Chandler’s first trial, Eileen and Keen grew certain she was innocent. They not only visited Chandler in prison, but they sold 500 acres of property and closed Keen’s law practice to devote their time and resources to Chandler’s case. And it was Keen who filed the 2016 ethics complaint that led to the Kansas Supreme Court overturning Chandler’s case and later disbarring Spradling, according to the Kansas Reflector.

Eileen was also the one who sent a “a relentless stream of unsolicited emails” to former New York Times and ProPublica journalist Joe Sexton, Vanity Fair reports.

Courtesy of HBO

“Obsessiveness is a double-edged sword, right?” Sexton, pictured (at left) with the Umbehrs above, told the magazine. “The obsessed can achieve remarkable things, and the obsessed can lead to terrible and wrongful outcomes. But there’s little doubt that they meet the definition of obsessed, and that’s not a healthy place to be. … They’re true believers, and they back it up with earnest and genuine work of integrity. Have they lost their minds a bit? I think even they would concede that’s possible.”

Eileen and Keen felt the sting of that double-edged sword. When Chandler bucked conventional legal guidance and chose to represent herself at her third trial, the Umbehrs pulled their support. “I think it was maybe the first time that they had reckoned with how much they had sacrificed,” A Killer Story director Matthew Galkin (One Night in Idaho: The College Murders) told Vanity Fair. “I think they took it as just the ultimate show of disrespect for the work that people had done for her.”

A Killer Story shows easy answers are elusive in Chandler’s case.

After delving into Chandler’s crime, Sexton is ambivalent about her culpability. Citing a lack of proof, he revealed to Vanity Fair he wouldn’t have convicted Chandler if he’d been a juror. “But that doesn’t mean at the same time, I don’t think she couldn’t have done it,” he added.

Indeed, HBO says three-part docuseries probes “true-crime obsession and the dangers of blinkered certainty in a case where the truth may never be known.”

Galkin, similarly, is “not in any way confident” one way or the other in the case. “Keen and Eileen say it in the first episode, you want justice for the victims, you want the bad guy to be put away forever, and you want to feel a sort of a sense of completion when you finish watching or reading a crime story,” he told the magazine. “And this case provides none of those things.”

A Killer Story, Series Premiere, Thursday, September 10, 9/8c, HBO & HBO Max