This is Hidden Killers with Tony Bruske.

Here now, Tony Bruske.

Walk the dog, scrawled in handwriting across the top of a six-page letter, hidden inside a L-Sat prep book and Corey Richon's jail cell.

Deputies found it while Corey was being treated for a medical episode. Inside, detailed

instructions for her mother, Lisa Darden, to coach her brother on what to say if he testified.

Have him tell the court Eric got drugs from Mexico, that Eric was an addict, that his death

was an accidental overdose, specific talking points, specific narrative,

specific scripts for another human being to deliver under oath. When prosecutors flagged it

as witness tampering, Corey didn't deny writing it instead on a recorded jail call with her mother,

she said, those papers were not a letter to you guys. They were part of a

freaking book. I was writing this fictional mystery book about her fictional stay in a Mexican prison.

She asked her attorney to smuggle in crest white strips because her teeth were getting yellow

from all the coffee they drink in the Mexican prison. That explanation is more revealing than the letter itself,

and this is where we leave the room's metaphor behind. Because what's happening here isn't

compartmentalization anymore. It is something faster, more automatic, more biological.

This is a reflex. And when you see it for what it is, the rest of her post-arrest behavior

stops being confusing and starts being a roadmap to how her brain is miswired.

Watch what happens when she gets caught.

She doesn't go silent, doesn't invoke her rights,

doesn't simply deny.

She generates a story instantly.

Under pressure, on a recorded line,

...