In May 2023, Mark Howerton is about to go on trial for the second time for the murder of Cayley Mandadi.
Taylor Clement: I felt confident that this was her time.
In the five plus years since Cayley's death, Howerton was active on social media, posting things like, "Come @ me legally, I'll beat you ..." — showing little remorse.
MARK HOWERTON (social video post): Wow. 75% of people think I'm guilty. That just means 75% of people in the world…can suck my d***.
Christy Jack: He was living large and bragging about having beaten the state of Texas in a court of law.
Howerton's attorneys John Hunter and Hallie Pease say acting out on social media was his way of coping with the pressure of being falsely accused of murder.
Hallie Pease: He was using social media as an outlet for — to relieve some of that tension.
During the first trial, jurors had only one charge to consider – felony murder. This time around, lawyers add more charges, including aggravated assault and criminally negligent homicide. Then came time to consider the video Cayley's parents had made.
Peter Van Sant: Did you want the jurors to see that video?
David Lunan: I did, initially.
Presenting the video came with risks, including the risk that Hunter's cross-examination about it might undermine the whole case.
Christy Jack: The judge said I'm gonna let it in. But if so … then the parents are now witnesses and they will no longer be allowed to sit in the trial. … And the prosecution went and talked to the parents, and they decided to withdraw the exhibit.
On May 23, trial two begins — this one without television cameras. Alessandra Cranshaw's opening argument is nearly the same.
Alessandra Cranshaw: I basically told the jury that … the best way to explain this case … is to start where Cayley Mandadi's life ended and that's in the car with this defendant.
But there is a big change to the witness list: no Jett Birchum.
Christy Jack: There was nothing to be gained.
And prosecutors add a witness - an expert on domestic violence who told jurors Howerton was a textbook abuser, who isolated and manipulated Cayley, and ultimately became enraged and lost control.
A pattern particularly difficult to handle at just 19 years of age.
Christy Jack: I think she had no idea, the dangerous predicament she was in.
John Hunter wants jurors to give Howerton the benefit of the doubt.
John Hunter: The … presentation of how Cayley looks in the hospital and how she looked at the autopsy does not mean that she was beaten.
His case, this time around, relies heavily on the testimony of a pharmacologist who said the high levels of MDMA, or ecstasy, in Cayley's system could have caused her brain bleed.
John Hunter: I have always felt that that was the major precipitating reason for her death.
But prosecutors and Cayley's family say Hunter grossly exaggerated the danger of MDMA.
Alison Steele: There's never been a single documented case anywhere of MDMA causing a subdural hematoma.
Peter Van Sant: What do you say to that?
John Hunter: Well, first of all, they haven't done much research on this at all.
Hunter plans one final witness — the former medical examiner whose testimony about organ donation and a possible skull fracture caused so much damage to the prosecution in the first trial — Dr. William Anderson.
This time, prosecutors are ready for him, with a new witness, a respected medical examiner who told them Anderson's claims in the first trial were irresponsible.
Alessandra Cranshaw: They realized that we were gonna be more than prepared to shoot down all those claims that he had made in the first trial.
John Hunter: I didn't need to have a fight about the skull fracture.
So the defense rests without Anderson.
Lawrence Baitland: It was a shock. … You could hear a gasp in the courtroom …
Now, a second set of 12 people will determine Mark Howerton's fate. It's an agonizing second wait for Cayley's parents.
Christy Jack: This is the moment of truth; will their daughter get justice?
Agonizing for John Hunter, too. He'd spent nearly six years working to keep Howerton free.
Peter Van Sant: So the jury comes back in, what do you hear?
John Hunter: The two most beautiful words in the English language, not guilty.
Peter Van Sant: Not guilty of murder.
Alison Steele: My heart sank when we heard not guilty on the murder.
Christy Jack: … they're thinking, dear God, this is the final nightmare. He's gonna walk outtalk the courtroom.
But there was more. Howerton was convicted of aggravated assault causing serious bodily injury.
David Lunan: Everyone was hugging each other and expressing their relief that Mark Howerton was going to prison.
Alison Steele: I turned to my left and eight sheriff officers had assembled to take him to jail. Eight. So, that was their way of saying, "we're here for you." (cries) So, that was a — that was a nice moment to see that.
Howerton was sentenced to the maximum – 20 years in prison. To Cayley's family, it's not nearly enough.
Lawrence Baitland: Mark Howerton is a monster, and he does what a monster does.
For Cayley's friend Taylor Clement, the wound remains raw.
Taylor Clement: I miss my best friend.
Baitland and Steele say they have no regrets about spending time and money on a video the jury never got to see.
Lawrence Baitland: It helped us learn what happened. … We would do it over again if we had to.
"48 Hours" showed Steele that video for very first time.
Alison Steele: It's hard to see because that's most likely the blow that killed her.
Cayley's mom, who prayed something good would come from her daughter's death, continues her fight to help other victims of violence.
Alison Steele: What I would like is for her sacrifice … to help other people. That's what she would want. I have absolutely no doubt about that.