Mad Over Stories Team
A note from the Mad Over Stories desk: every case below is real, every fact below is sourced to public reporting, and every theory below is clearly labelled as a theory. We don’t name suspects who haven’t been charged.
“Unsolved” is a strange word in true crime. It rarely means nobody has any idea what happened. Usually it means investigators have a theory they can’t prove, a suspect they can’t charge, or evidence that keeps pointing in two directions at once. The cases that haunt people are the ones where the facts are public, the timeline is detailed, and the answer is still missing.
This is a tour of five of the most baffling unsolved cases from the last decade — roughly 2015 to 2025. We picked them not because they’re the most gruesome or the most viral, but because each one teaches you something about why some cases never close. If you’d like the wider context for why we keep coming back to stories like these, our guide on the true crime documentary genre covers how the field reports them, and the companion piece on the psychology of true crime obsession covers why we can’t let them go.
1. The Delphi murders — Indiana, 2017
On 13 February 2017, 13-year-old Abigail Williams and 14-year-old Liberty German went for a walk on the Monon High Bridge near Delphi, Indiana. They never came home. Their bodies were found the next day in woodland on the other side of the river.
What made Delphi different from a typical small-town homicide investigation was that Liberty German had filmed the suspect on her phone. A short, low-quality video showed a man in a dark jacket and jeans walking on the bridge, and a now-infamous audio clip captured his voice saying “down the hill.” Indiana State Police released both, hoping someone would recognise the man. Tens of thousands of tips came in. None of them closed the case for nearly six years.
An arrest was finally made in October 2022, and a trial concluded in 2024 — but the case remains the textbook example of how forensic evidence, eyewitness identification and a viral suspect description can take years to converge. The five-year information gap, the leaks, the multiple sketches released by police, and the question of how this happened in broad daylight on a busy bridge will keep this case in true crime conversations for a generation.
Why it’s baffling: the suspect’s image, voice and a precise timeline were public almost immediately. The case still took nearly six years to charge.
2. The disappearance of Brian Shaffer — earlier case, new evidence in 2018 and 2022
Brian Shaffer was a 27-year-old Ohio State University medical student who walked into a bar in Columbus on the night of 31 March 2006 with friends, was filmed on CCTV entering the building, and was never seen leaving. Although the original disappearance is older, two waves of new tips, civilian investigations and re-examinations in 2018 and again in 2022 placed the Shaffer case back at the centre of unsolved-case discussion.
The bar — the Ugly Tuna Saloona — had a single entrance and exit, both covered by CCTV. Every other patron and staff member was eventually accounted for on the tapes. Shaffer was filmed entering and never filmed leaving. There is no service exit footage, no obvious blind spot, and no body. It is one of the cleanest “locked room” disappearances in the modern record.
Civilian sleuths have, over almost two decades, produced floor plans, timed reconstructions and entire podcasts arguing for everything from a quiet exit through a construction zone to a foul-play scenario involving someone Shaffer knew. Police have publicly said they have a working theory; they have not publicly said what it is.
Why it’s baffling: the CCTV is excellent and the geometry is small. There is nowhere for the answer to hide, and yet it is hiding.
If you find the locked-room version of the missing-person genre compelling, our long-read on the man who vanished in 1987 and the credit-card receipt that surfaced 32 years later sits very close to this case in spirit.
3. The murders of Kristin Smart’s suspect timeline — California, 2016 reopening
The disappearance of 19-year-old Kristin Smart from Cal Poly San Luis Obispo in 1996 was reopened by the San Luis Obispo County Sheriff in 2016 with a new lead investigator, a new search of properties associated with the long-time suspect Paul Flores, and a multi-year journalistic effort centred on the podcast Your Own Backyard.
For most of the case’s first two decades, the original suspect was effectively the only suspect, but no body had ever been found and no charges had ever been filed. The 2016 reopening produced new physical searches, a federal indictment in 2021 of Flores and his father, and a conviction in 2022. But Smart’s remains have still never been recovered, which means a legally closed case sits next to a forensically and emotionally open one.
The Smart case is the clearest example in modern true crime of an unsolved case being moved by sustained civilian and journalistic pressure rather than by new forensic technology. It is also a quietly important reminder that “convicted” and “solved” are not the same word.
Why it’s baffling: the conviction came, but the most basic question — where is she — is still open.
4. The Long Island serial killer — Gilgo Beach, ongoing
Between 2010 and 2011, the remains of 11 people were found along the Ocean Parkway on Long Island, New York. The remains were later linked, the case became known as the Long Island Serial Killer (LISK) or Gilgo Beach murders, and for more than a decade it was the single most prominent unsolved serial-killing investigation in the United States.
An arrest was finally made in July 2023: a Massapequa Park architect named Rex Heuermann, charged in connection with several of the victims and indicted further in 2024 and 2025. Even with the arrest, the case is not closed — it covers more than a decade of victims, multiple investigative agencies, allegations of police misconduct in the original 2010–2011 investigation, and unanswered questions about whether all of the Gilgo Beach victims share a single offender.
What makes LISK exemplary as an unsolved-case study is the 13-year gap between the discovery of the remains and the first arrest, despite an enormous amount of physical evidence — burner phones, vehicle records, witness reports — having been compiled almost from the start. Police later acknowledged that the original investigation had been compromised by internal dysfunction, including the conduct of a former Suffolk County police chief who was himself convicted of unrelated crimes.
Why it’s baffling: the evidence was there. The institutional will to act on it wasn’t.
5. The McStay family murders — California, 2010 discovery, conviction 2019, theories ongoing
In February 2010, Joseph and Summer McStay and their two young sons disappeared from their home in Fallbrook, California. Their car was found near the Mexican border, food was left out on the kitchen counter, and surveillance footage appeared to show four figures crossing into Tijuana. For three and a half years the public-facing investigation operated on the assumption that the family had voluntarily moved to Mexico.
In November 2013, the bodies of all four members of the McStay family were found in shallow graves in the Mojave Desert. Joseph McStay’s former business associate Charles Merritt was arrested in 2014, tried in 2019, and convicted of all four murders. The case is legally closed.
And yet — the McStay case is on this list because the path from “they walked into Mexico” to “they were murdered in the desert” exposes a kind of unsolvedness that doesn’t go away when the trial ends. The original missing-persons investigation produced almost three years of public reporting based on a theory the evidence eventually contradicted. Journalists, the family’s relatives and at least two book-length investigations have continued to ask, openly, whether the conviction sits on a complete account of what happened that week in 2010.
“Solved” is a moving target in true crime. The McStay case is one of the clearest reminders of that in the last fifteen years.
Why it’s baffling: the conviction is in. The narrative of the first three years was wrong. Both are true.
What these five cases have in common
If you read these one after another, the same patterns surface again and again.
Evidence is rarely the bottleneck. Delphi had video and audio. Shaffer had CCTV. LISK had phones and vehicles. McStay had a fully searchable digital trail. In every case, the question wasn’t whether the evidence existed — it was whether anyone could act on it.
Institutional friction does the most damage. Three of the five cases involved a police force or prosecutor’s office that publicly or privately acknowledged structural problems in the original investigation. When unsolved cases finally move, it’s often because someone outside the original agency forced the movement.
Civilian and journalistic pressure increasingly matters. Podcasts, long-form reporting and obsessive online communities have measurably shortened the time-to-arrest in the modern unsolved-case landscape. That’s a double-edged sword — innocent people get named, families get re-traumatised — but the trend is now part of the system.
“Unsolved” is a spectrum. Some of these cases have no suspect. Some have a suspect and no body. Some have a conviction and no story. The genre uses one word for all of them, and that’s part of why true crime fans never quite feel done with the cases on this list.
If you want the wider lens on why these stories grip us — what your brain is actually doing when you stay up reading reconstructions of a stranger’s missing-person timeline — our companion piece on the psychology of true crime obsession is the natural next read. And for an example of how the same investigative instincts apply to non-criminal mysteries, the deep-sea recording researchers refused to release for 11 months shows the form working a different beat.
Read more: the complete guide to the world’s greatest unsolved mysteries.
Read more: a small town that kept a burial secret buried under its park for 23 years.
Frequently asked questions
What does it mean for a case to be “unsolved”?
In US and UK criminal practice, a case is generally considered unsolved if no one has been charged, or charges have been dismissed, or a charged suspect has been acquitted. Convictions can be obtained without the case being fully solved — the McStay family case, for example, ended in a conviction without ever fully accounting for the first three years of the investigation’s official narrative.
Which is the most famous unsolved true crime case of the 2010s?
The Delphi murders (2017) generated more sustained national news coverage in the United States than any other case on this list during the 2010s, in large part because Liberty German’s phone captured both video and audio of the suspect. The Long Island Serial Killer investigation was the most prominent unsolved serial case of the same decade.
How are unsolved cases reopened?
Cases are typically reopened for one of three reasons: new forensic technology (often improved DNA testing), new witness testimony, or sustained outside pressure from journalists, podcasters or civilian investigators. Three of the five cases above moved because of the third route — not new evidence, but new attention forcing a fresh look at evidence that had been sitting in storage.
Should amateur sleuths get involved in active cases?
Police, victims’ families and journalism researchers generally agree that civilian interest is a net positive when it stays within ethical bounds — sharing public information, fundraising for searches, supporting families — and a net negative when it crosses into naming suspects, harassing witnesses or contaminating evidence. The Delphi and LISK cases both produced examples of each.
Where can I find reliable updates on unsolved cases?
The most reliable sources are court filings (PACER in the US), local-newspaper crime reporting, and a small number of long-running journalism-led podcasts that cite their sources. Sensationalist YouTube and TikTok accounts often repeat, mix and exaggerate older theories. As a habit, check the date and the source on any “new development” before sharing it.
