Cayley Mandadi, 19, was a typical Texas teenager navigating life through school, sports and boys. Friends say she had a big heart and was "full of love." Her mother says Cayley was a happy person who was trusting, warm and always smiling.
Mandadi was a sophomore studying communications at Trinity University, a small liberal arts college in San Antonio, Texas. In the fall of 2017, friends say Mandadi finally felt like she was fitting in at school. She joined a sorority and was a member of the Trinity cheerleading team.
Mandadi dated Trinity student and football player Jett Birchum her freshman year. But the relationship was on again, off again.
A new man in Mandadi's life
There was another man in Mandadi's life – 22-year-old Mark Howerton. Growing up, Howerton had been a star high school baseball player. Howerton was not a student at Trinity, but often visited his friends on campus. That's how he met Mandadi. By October 2017 their friendship turned into a romantic relationship.
A rocky relationship
Howerton and Mandadi's relationship quickly turned rocky. According to campus police, a few weeks before her death, Howerton tore apart Mandadi's dorm room. After having an argument, Howerton reportedly threw her clothes in the trees, cracked a sliding glass door and later smashed her laptop. The Trinity University Police Department was called to the scene and Howerton was banned from campus.
A weekend of partying
The last weekend of October 2017 Mandadi and Howerton attended the Mala Luna Music Festival in San Antonio. The couple took MDMA, a drug known as Molly or ecstasy. This photo was taken at the music festival.
According to Howerton, on Sunday, Oct. 29, 2017, the couple left Mala Luna sometime after 4 p.m. They got in an argument after seeing Mandadi's ex-boyfriend, Jett Birchum, at the festival.
Howerton said they continued to argue in the car, but eventually stopped at a parking lot to have "rough" make-up sex. Howerton would later tell police that sometime after having sex, Mandadi stopped breathing. At some point he brought her to the emergency room.
A disturbing scene
When Howerton arrived at the emergency room, Mandadi was in the passenger seat of his car, nearly naked and unconscious. A paramedic testified that she saw "multiple bruises" on Mandadi's legs and immediately started CPR.
Mark Howerton's hands
While doctors tried to save Mandadi's life, officers on the scene interviewed Mark Howerton about what happened that night. They took this photo of his hands,
Mark Howerton arrested
Three months after Mandadi's death, her autopsy report was released. It showed that she died from blunt force trauma to the face and head, and labeled her death a homicide. Several weeks later, Howerton was arrested and charged with murder and sexual assault. He pleaded not guilty and was released on bail.
Defending Mark Howerton
In December 2019, Howerton went on trial in San Antonio for the murder of Mandadi.
"This is a case where, there's more than meets the eye and things aren't what they seem," John Hunter, Howerton's defense attorney, told "48 Hours."
Mandadi's ex-boyfriend takes the stand
During the trial, Birchum, told the jury what he witnessed at the Mala Luna Music Festival. He testified that he saw Howerton and Mandadi "having an intense conversation" and Mandadi "trying to create space" and "get away." He said he then witnessed Howerton, "reach out his right arm and hook it around her shoulder and pull her in closer. And then turn and walk away."
During cross-examination, Hunter grilled Birchum about what he says he saw that day. Birchum originally told police that he saw Howerton pick Mandadi up and put her in his car as they were leaving the festival. On the stand, Birchum admitted to misleading police about this, testifying that he didn't actually see Howerton put Mandadi in his car.
The defense theory
The defense presents a different theory of how Mandadi sustained her injuries that day. They argue Mandadi's bruises were at the hands of the medical staff and not Howerton. They say the cause was from the organ donation process and when medical professionals desperately tried to revive Mandadi seven times, they broke one of her ribs and bruised her body.
A hung jury pushes Mandadi's parents to start their own investigation
After 10 hours of deliberations over two days, the jury notified the judge that they were unable to come to a decision. A mistrial was declared.
While prosecutors planned to retry Howerton, Cayley's mother Alison Steele (pictured) and stepfather Lawrence Baitland decided the jury needed more information about what happened inside Howerton's car.
Mandadi's parents develop their own theory
Steele and Baitland focused on an autopsy photo showing a bruise in the shape of a small dot above Cayley's right ear and another larger bruise above Cayley's left ear.
Steele says they believe Cayley's fatal injury took place when Howerton "reached from his driver's seat, hit her in the left ear and drove her head into the window and onto the lock button of the car."
Steele and Baitland went to a used car lot where Steele posed in a car like the Mercedes Howerton drove the night Cayley was killed. This is one of the many photos Baitland took of Steele posing in the car. He told "48 Hours" he "photographed her head in different positions while … holding the autopsy images, trying to see if they match up with the door and it's a near perfect match."
Mandadi's stepfather develops a 3D model
Emboldened by the photos he took, Lawrence Baitland, a NASA engineer, constructed a 3D model of Mandadi's head. He layered in photos of Cayley and the autopsy photo showing that dot above Cayley's right ear.
"So this gave me the confidence to go to the next step, which was to seek out the killer's car," Baitland said.
Tracking down the alleged killer's car and commissioning a reenactment video
Bailtland tracked down Howerton's Mercedes. He convinced the owner to sell him the car.
Baitland and Steele then hired a private investigator who produced a reenactment video of what they believe happened in the car with actors similar in size to Mandadi and Howerton. This is a still frame of that video.
Howerton found guilty of aggravated assault at his second trial
Howerton is seen attending court at the start of his second trial in May of 2023.
The prosecution decided not to enter Steele and Baitland's reenactment video into evidence, concerned that the defense cross-examination about it might undermine the case.
The jury did not find Howerton guilty of murder, but rather aggravated assault causing serious bodily injury. He was sentenced to the maximum 20 years in prison. He is eligible for parole in May of 2033
Mandadi's parents continue to fight for victims
Alison Steele turned her grief into action. In September 2019, she was able to get the CLEAR Alert Bill passed. Now in the state of Texas when someone between the ages of 18-64 goes missing, an emergency text will go out to the community. Steele wants "Cayley's story to be used to help other people."
Taylor Clement will never forget her best friend. She told "48 Hours" that she had always planned to have Mandadi as her maid of honor in her wedding someday, and the godmother to her future children. She said this photo of them "smiling at prom is [her] absolute favorite."