How Key Evidence Derailed a 40-Year-Old Child Murder Trial

Kathleen Flynn took the same wooded path every day after school from Ponus Ridge Middle School to an intersection in Norwalk, Conn., to meet her mom, Esther Flynn, who worked as a math teacher at a nearby high school.

On September 23, 1986, the 11-year-old, who had been a sixth grader for only a few weeks, had plans that afternoon to go shopping for a new purse with Esther.

But Esther was running late to their meetup spot due to a work meeting, and when she arrived, Kathleen was nowhere to be found.

Esther searched everywhere but was soon forced to file a missing person’s report when her daughter never turned up.

At 2 a.m. on September 24, 1986, police found Kathleen’s clothing and school bag in the woods. An hour and a half later, her half-naked body was recovered under a pile of brush.

It was apparent she had been bound at the wrists, strangled to death and sexually assaulted.

Marc Karun, a convicted sex offender who was 21 at the time of Kathleen’s murder, was identified as a suspect early in the investigation.

He lived two miles away from the scene, used similar ligatures in a previous sexual assault in January 1986, and his green 1970 Chevrolet was allegedly spotted in the area at the time Kathleen went missing.

Speaking with detectives, Karun claimed he was at Ponus Ridge Middle School four days before the incident, visiting some teachers, the librarian and walking “on the wooden path that led to Hunters Lane.”

His claim of meeting with school staff that day was later disproved, according to authorities.

The morning of the murder, he alleged he was out looking for work and denied having any involvement in the crime but still appeared nervous, police noted.

At the time, there was no evidence or further information connecting Karun to the deadly rape, and the case eventually went cold.

However, he continued to remain the primary suspect.

Eight months before Karun was suspected of raping and killing Kathleen, he sexually assaulted an 18-year-old girl he knew from high school, according to court records. He was charged with first-degree sexual assault, which was later downgraded to sexual assault in the fourth degree after the victim declined to testify in court.

He was later convicted of a pair of sexual assaults in 1988 and sentenced to 16 years with six years in prison and 10 years probation. Two counts of kidnapping and one count of unlawful restraint were dropped that same year.

Karun’s extensive criminal history also includes threatening, burglary and larceny.

In 2012, authorities turned their attention back toward Karun, citing advances in DNA technology. However, the DNA found under Kathleen’s fingernails came back inconclusive.

Further advances led investigators back to Karun in 2017 to procure more DNA samples to test against evidence. The alleged results, coupled with similarities to Karun’s previous cases, led to his arrest on charges of the sexual assault and murder of Kathleen. In 2019, he was taken into custody at his home in Stetson, Maine, where he had been living for about six years as a registered sex offender.

Karun’s trial was hindered by federal weapons charges after authorities recovered nearly 90 firearms and thousands of rounds of ammunition at his home in Maine during his arrest in 2019.

Karun is prohibited from gun possession due to his convicted felon status.

He pleaded guilty to federal gun charges in 2024, and his trial for Kathleen’s murder commenced March 30, 2026.

On the first day of the trial, Kathleen’s mom Esther testified that she reported Kathleen missing and that her husband and brother positively identified Kathleen’s body the next morning.

Three former police officers also took the stand.

But one week in, Judge John Blawie declared a mistrial over possible evidence contamination after a retired Norwalk police lieutenant said that forensic scientist Henry Lee told him Kathleen was placed in a used body bag.

Lee prominently worked on the O.J. Simpson and JonBenét Ramsey cases. He died in March 2026 at the age of 87.

While Blawie said he is not dismissing the case, “essentially, all five days of testimony are wiped from the record, so to speak,” Scott DeVito, associate professor of law at Quinnipiac University, tells A&E Crime + Investigation.

The prosecution was relying on trace DNA to prove Karun is the perpetrator. The problem with reusing a body bag is someone else’s DNA may have already been in there, DeVito explains.

“There's already very little DNA” investigators are working with, “and that means it's very easy for extraneous DNA to come in and make that trace DNA give false results,” he says.

During the trial, a state crime lab official testified that the DNA found under Kathleen’s fingernails was 22,000 times more likely to belong to her and Karun, rather than her and another person.

Still, prosecutors are now tasked with proving the body bag was not reused in this instance. If they succeed, “that would probably lead to a new trial, but if they can't definitively show that, we may not get one,” DeVito says.

Prosecutors are also likely weighing other options, such as a plea agreement.

“They're probably going to attempt to negotiate, because what's going to have to happen now to prosecute him is they're going to have to re-prosecute him from scratch,” DeVito explains. “They might not want to put those witnesses back through that very painful experience of having to recount what happened.”

But the success of winning the conviction the state is seeking relies on solid DNA evidence.

“If at the end of the day you don’t have it, he’s [Karun’s] probably going to—at least for now—walk away, even if he was the actual perpetrator,” DeVito adds.

Karun remains held on $5 million bond.