Some true-crime stories are built around discovering who committed a murder.
HBO’s A Killer Story is interested in a more uncomfortable question.
What happens when everyone becomes convinced they already know?
The new three-part documentary series examines the extraordinarily complicated case of Dana Chandler, whose former husband Mike Sisco and his partner Karen Harkness were found murdered in Topeka, Kansas, in 2002.
More than two decades later, the legal battle surrounding those deaths has included three trials, a conviction overturned because of prosecutorial misconduct, a hung jury and another guilty verdict.
Yet the case remains surrounded by questions.
HBO has released the official trailer for A Killer Story, which premieres September 10 and follows investigative journalist Joe Sexton as he attempts to understand not only what happened to Sisco and Harkness, but how radically different groups of people came to believe completely different versions of the same story.
At the centre is Dana Chandler.
Prosecutors argued that Chandler, Sisco’s ex-wife, was motivated by jealousy and anger over the end of their marriage and his new relationship with Harkness.
The case against her was largely circumstantial.
No DNA evidence tied Chandler to the murders.
No fingerprints placed her at the crime scene.
No murder weapon was recovered.
Nevertheless, Chandler was arrested in 2011 and convicted of the killings the following year.
For years, that appeared to be the conclusion.
Then the case began to unravel.
In 2018, the Kansas Supreme Court overturned Chandler’s convictions after determining that prosecutors had presented materially false or misleading testimony during the original trial.
That decision did not declare Chandler innocent.
It meant the state would have to prove its case again.
And that is where A Killer Story becomes considerably more complicated.
The documentary follows Eileen and Keen Umbehr, a Kansas couple who became convinced Chandler had been wrongfully convicted.
They were not investigators.
They were not relatives.
They were ordinary people who became deeply involved after studying the case and concluding that the evidence did not support the narrative presented at trial.
Their interest eventually developed into something much larger.
The Umbehrs contacted journalists, studied records, challenged the prosecution’s theory and focused heavily on another person they believed investigators had failed to examine sufficiently.
Their certainty about Chandler’s innocence eventually caught the attention of Joe Sexton, a veteran investigative journalist and former New York Times editor.
Sexton initially entered the story because of the persistence of the people contacting him.
Then he began asking his own questions.
Director Matthew Galkin followed that investigation for approximately six years.
The result is not structured simply as another documentary attempting to prove that a convicted person is innocent.
Instead, A Killer Story appears deliberately suspicious of certainty itself.
That applies to prosecutors.
It applies to defence advocates.
And it applies to the enormous true-crime audience watching from outside the courtroom.
HBO describes the series as exploring family conflict, betrayal, prosecutorial misconduct, competing narratives and confirmation bias.
Those final two ideas may be the most important.
Once someone develops a theory about a crime, every new piece of information can begin looking like proof.
Evidence supporting the theory becomes important.
Evidence contradicting it becomes explainable.
Coincidences become suspicious.
Missing information becomes evidence of conspiracy.
And eventually, changing someone’s mind may become harder than solving the crime itself.
That problem sits underneath almost every stage of the Chandler case.
The original prosecution presented Chandler through one of crime storytelling’s most familiar archetypes:
The jealous ex-wife.
According to that theory, she could not accept Sisco’s relationship with Harkness and ultimately killed them both.
The narrative was emotionally understandable.
But A Killer Story asks whether an understandable narrative is necessarily an accurate one.
The documentary also examines the people who became equally convinced of the opposite conclusion.
For the Umbehrs, evidence overlooked or interpreted differently suggested Chandler had been wrongly accused.
Their advocacy helped keep scrutiny on the case after her original conviction was overturned.
But HBO’s series does not appear prepared to replace one simple story with another.
That becomes especially important as Chandler returns to court.
Her second trial, held in 2022, did not produce a verdict.
The jury could not reach a unanimous decision.
That resulted in a mistrial.
For most criminal defendants, two trials across a decade would already represent an extraordinary legal journey.
Dana Chandler faced a third.
By then, the case had become something far larger than the original murder investigation.
Journalists were involved.
True-crime advocates were involved.
Questions about prosecutorial conduct had become part of the record.
Competing theories had circulated for years.
And people on every side had spent enormous amounts of time constructing explanations for what happened in 2002.
The third trial introduced one more extraordinary development.
Chandler chose to represent herself.
She dismissed her legal team and faced the prosecution without conventional defence counsel controlling her case.
In 2025, the jury again found her guilty.
That verdict provides legal finality.
But HBO makes clear that legal finality is not necessarily the same thing as answering every question raised during the previous two decades.
That distinction is what gives A Killer Story its title.
There is the murder story.
There is the prosecution’s story.
There is Dana Chandler’s story.
There is the story believed by the Umbehrs.
There are stories constructed by investigators, jurors and journalists.
And eventually there is the story audiences create after watching all of them.
Each version determines which details appear important.
The documentary’s three episodes follow that evolution.
Chapter One, “The Jealous Ex-Wife,” examines the original investigation, Chandler’s first conviction and the narrative that initially persuaded a jury.
That conviction is eventually overturned.
Chapter Two, “Person of Interest,” follows the retrial and the alternative suspect championed by Chandler’s supporters, while prosecutors continue arguing that Chandler had motive and opportunity.
A surprise witness changes the direction of the proceedings, but the jury ultimately cannot agree.
Chapter Three, “A Dangerous Notion,” follows the third prosecution, Chandler’s extraordinary decision to represent herself and the verdict that finally concludes the courtroom battle.
Yet the documentary appears deliberately unwilling to tell audiences what they should believe when the credits roll.
That may distinguish A Killer Story from a large portion of modern true crime.
The genre frequently builds momentum around revelation.
A suspect is exposed.
Evidence is uncovered.
A theory is disproved.
A mystery receives an answer.
This case resists that structure.
There may never be a single piece of forensic evidence capable of ending every argument.
Instead, viewers are asked to examine how people decide what they consider believable.
That includes the investigators who originally pursued Chandler.
The prosecutors who repeatedly brought the case to court.
The jurors asked to determine guilt beyond reasonable doubt.
The citizen advocates convinced the wrong person had been accused.
And journalists attempting to establish what can actually be proven.
Director Matthew Galkin previously worked on documentaries including Kevorkian and One Night in Idaho: The College Murders.
A Killer Story is produced by Story Syndicate in association with Concordia Studio and Fairhaven.
Joe Sexton also serves as producer, while executive producers include Joshua Levine, Dan Cogan, Liz Garbus, Jon Bardin, Kate Barry, Julie Gaither, Davis Guggenheim, Jonathan Silberberg and Nicole Stott.
For HBO, Nancy Abraham, Lisa Heller and Tina Nguyen executive produce.
Featured participants include Sexton, Eileen and Keen Umbehr, witness Terri Anderson, jurors and others connected to the case.
But the series is ultimately about something broader than one murder trial.
True crime encourages audiences to become investigators.
Documentaries present evidence.
Podcasts develop theories.
Online communities compare timelines.
Viewers decide who sounds credible.
And occasionally people become so invested in one explanation that changing their minds becomes almost impossible.
A Killer Story asks what happens when that instinct collides with an actual criminal case where people's lives depend on the answer.
Mike Sisco and Karen Harkness were murdered.
Dana Chandler has been convicted of killing them.
Those facts now exist alongside decades of disputed evidence, courtroom reversals and people on opposing sides who remain convinced they understand what really happened.
HBO’s documentary does not promise to make that uncertainty disappear.
It asks viewers to examine how it was created.
A Killer Story premieres September 10 on HBO and HBO Max.
New episodes debut weekly through September 24.
Watch the official trailer below.
