MISSING: Melissa Casias

Episode of Crime Junkie · April 27, 2026 · 1 h 32 min

Ashley Flowers and Brit Prawat examine the June 2025 disappearance of Melissa Casias in Taos, New Mexico, and the family feud over whether she left voluntarily.

Summary

Ashley Flowers presented the case of Melissa Casias, a Los Alamos National Laboratory administrative assistant who vanished on June 26, 2025, after dropping her husband Mark at work and returning to her Taos County home. She left behind her wallet, keys and work phone, while both personal phones had been factory reset and her iCloud account scrubbed. The episode drew on the 911 call, a recorded phone call between Mark and Melissa's sister Trudy, and interviews with both sides of a divided family: the Casias household, who believe she walked away, and the Mondragons, her parents and siblings, who suspect foul play and Mark's involvement.

Flowers detailed early evidence including muddy boots, a presumptive blood stain, the couple's severe debts and suspended security clearances, and a tip from an acquaintance named Lloyd that police initially ignored after Mark dismissed it. Mark later found home surveillance video showing Melissa walking alone along Highway 518 at 2:18 p.m. Flowers argued that the staggered phone resets indicated Melissa acted with a plan, while criticizing the investigation, playing in full a bodycam interview in which Agent Ezekiel Esquivel-Mata briefly questioned Rick Valerio, a man with a blue Dodge truck who allegedly claimed to have found a decapitated body.

The hosts also discussed a mysterious Colorado friend who reportedly visited Melissa's daughter Sierra and later denied it to police, and a theory circulating online linking Melissa to a list of missing or dead people connected to Los Alamos and NASA, which Flowers said was probably not the answer. Flowers concluded that the simplest explanation was voluntary departure, but urged investigators to obtain app location data via exigent-circumstances requests, and shared a New Mexico State Police tip line.

Chapters

0:33
Introduction
Flowers explains that a listener's email led the show to a case in which Melissa Casias's family is split over what happened to her.
2:17
The day Melissa vanished
Sierra discovers her mother missing, with her belongings left behind and both personal phones factory reset, and Mark calls state police.
8:21
Timeline and missing items
Mark and Sierra lay out the day for police, and a 90-day supply of thyroid medication and a few personal items are found missing.
12:10
The Mondragons, Diego and Lloyd's tip
Melissa's family arrives, names Sierra's ex-boyfriend Diego as a suspect, and relays a sighting of Melissa on Highway 518 that police decline to check after Mark dismisses it.
18:58
Boots, blood and finances
Investigators find muddy boots and a presumptive blood stain while Mark offers shifting theories rooted in the couple's collapsing finances.
26:21
Recorded calls and the Highway 518 video
The Mondragons record Mark, and Mark later locates surveillance footage showing Melissa walking alone along Highway 518.
42:06
Mark's side and the wiped phones
Mark disputes allegations against him, and forensic evidence shows Melissa's phones were wiped hours apart and her iCloud scrubbed.
50:00
A family divided
Both sides accuse each other over past relationships, the search effort, and the mishandled Lloyd tip.
53:05
The Rick Valerio tip
A tourist's report of a man claiming to find a decapitated body leads to a brief police interview, played in full.
59:49
Gaps in the investigation and theories
Flowers questions how leads were cleared, reviews searches, Mark's job-contact theory and a mysterious Colorado friend, and the police view that Melissa likely left.
1:13:02
The missing scientists theory
Flowers discusses a list of missing or dead people tied to Los Alamos and NASA on which Melissa's name has appeared.
1:22:34
New curveballs and phone data
The Colorado friend denies the visit, and Flowers advocates using app location data obtained under exigent circumstances before closing with a tip line.

Key points

What was said, by whom, with the exact words. Timestamps jump to the moment.

Linked moment · 8:01Skip to 8:01 using a listen link in the info box.
Mark Casias
Mark Casias told dispatch that his wife would never have wiped the photos and information from her phone.
“she would never have wiped all the pictures off and all the information off of her phone”
Listen from 8:01 · Factory reset and iCloud data erasure
Ashley Flowers
Flowers criticizes police for declining to follow up on Lloyd's sighting simply because Mark said it was not Melissa.
“The biggest WTF moment for me is that police just go along with it. No need to check that out”
Listen from 17:21 · New Mexico State Police
Mark Casias
Mark Casias argued in a recorded call that any blood in the house would mean he harmed Melissa before work, which the timeline contradicts.
“If there was a drop of blood, if there was blood in this house, that means I would have had to hurt Melissa before we left to work”
Listen from 28:56 · Disappearance of Melissa Casias
Ashley Flowers
Flowers says the hours-apart wiping of Melissa's two phones, more than anything else, suggests Melissa had a plan.
“This is the detail, more than anything else, that makes me think Melissa had some kind of plan”
Listen from 46:33 · Factory reset and iCloud data erasure
Ashley Flowers
Flowers reasons that a third party wiping the phones would likely have wiped both at the same time.
“my gut tells me that if someone else wiped the phones, I would think that they would have wiped them both at the same time, right?”
Listen from 47:00 · Factory reset and iCloud data erasure
Ashley Flowers
Flowers believes the investigation's lack of robustness has deepened the divide between the two families.
“a huge part of why I think there is such a great divide between families is that the investigation has not felt robust”
Listen from 53:12 · New Mexico State Police
Rick Valerio
Rick Valerio told Agent Mata he did not know Melissa and denied finding any body.
“No, I don't even know her. I'm already dead to her”
Listen from 58:08 · Disappearance of Melissa Casias
Ashley Flowers
Flowers says the Rick Valerio interview makes her question what police mean when they say a lead was cleared.
“Because when they say that a lead went nowhere or that they cleared someone, I question what that means”
Listen from 59:49 · New Mexico State Police
Ashley Flowers
Flowers suggests society holds mothers to a different standard, making it hard to accept a mother leaving.
“I feel like mothers have this different societal expectation than father or like men do”
Listen from 1:11:36 · Voluntary disappearance
Ashley Flowers
Flowers argues the phone and iCloud wipes make suicide an unlikely explanation.
“I don't think you need to wipe your phone and your iCloud if your plan is just to take your own life”
Listen from 1:12:49 · Factory reset and iCloud data erasure
Ashley Flowers
Flowers believes that if Melissa walked away, she needed someone's help to do it.
“no matter what, if she walked away, I think she needed someone's help to do that”
Listen from 1:18:39 · Voluntary disappearance
Ashley Flowers
Flowers believes something troubling is happening to aerospace workers but doubts it explains Melissa's case.
“while I absolutely believe that something scary is happening to people who work in aerospace sciences, it's probably not the solution that we're looking for in Melissa's case”
Listen from 1:20:53 · Missing scientists conspiracy theory
Ashley Flowers
Applying Occam's razor, Flowers concludes the simplest explanation is that Melissa left on her own.
“The simplest explanation is that she chose to walk away and did it on her own”
Listen from 1:22:56 · Voluntary disappearance
Ashley Flowers
Flowers doubts Sierra would fabricate the Colorado friend's visit given how close she was to her mother.
“Sierra and her mom were so close. I cannot imagine why on earth she would ever make anything like that up”
Listen from 1:24:48 · Disappearance of Melissa Casias
Ashley Flowers
Flowers asserts that investigators can obtain app location data from companies without a warrant.
“even though like there's this common belief that you have to have a warrant to get that data from those companies, that is not true”
Listen from 1:29:26 · Exigent circumstances requests for app location data
Ashley Flowers
Flowers recommends families of missing people push detectives to pursue app-based phone location data.
“I would encourage anyone whose loved one vanished with their phone in the social media age to press their detective to look into this”
Listen from 1:33:17 · Exigent circumstances requests for app location data

People

In the conversation

Ashley FlowersCreator and host of the true crime podcast Crime Junkie and founder of Audiochuck
Brit PrawatCo-host of Crime Junkie, introduced in the episode as 'Britt'
Mark Casias
Rick Valerio

Discussed

Sierra CasiasDaughter of Melissa Casias who last saw her on June 26, 2025
JasmineMelissa Casias's niece who contacted Crime Junkie about the case
Diego MartinezSierra's ex-boyfriend, subject of a restraining order, initially named by Melissa's family
LloydLongtime acquaintance who reported seeing Melissa on Highway 518
Chris SweckerFormer FBI assistant director who has called for investigating links among missing scientists
Anthony ChavezRetired Los Alamos employee who disappeared in May 2025
Monica RezaNASA-affiliated woman who vanished while hiking in California in June 2025
William Neal McCaslandRetired U.S. Air Force major general who went missing in Albuquerque in February 2026
Amy EskridgeScientist on the list of deceased researchers cited in online theories
Michelle Hundley SmithNorth Carolina mother missing since 2001 who was found alive in 2026
Candace CooleyCanine search handler and founder of the nonprofit Dylan's Legacy

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From the publisher

In June 2025, Melissa Casias dropped her husband off at work in Los Alamos, New Mexico… then did something nobody expected. She turned around and drove home. By that afternoon, she had vanished, leaving behind her wallet, her keys, both of her personal phones wiped to factory settings, and a family already splitting in two over what to believe. Her husband, Mark, insists she walked away on her own. Her parents and siblings are certain something far worse happened to her. Surveillance video proves she was alive walking along Highway 518 that day. But where she went next - and why - is a question that only deepens the further you pull at it.

Summary, chapters and key points were generated from the episode transcript on September 27, 2026. Quotes are checked word for word against the transcript.

Categories: True Crime