Here's CBS' description of the hourlong "48 Hours" episode:
The investigation into what happened – driven by Pelle Wall's refusal to give up – reveals a family fractured by divorce, affairs, allegations of abuse, lingering anger between the husband and wife, and a son who eventually decided his father, Johnny Wall, had a hand in his mother's death. To get people to believe him, Wall, who was 17 at the time of his mother's death in 2011, risked everything, including his relationship with his father and future financial security.
"As I thought about my dad's behavior before and after her death – it became more and more apparent to me that – that he was responsible for killing her," Pelle Wall, tells Spencer.
Could he get anyone to listen? And how could he prove what his gut was telling him?
Von Schwedler, a university research scientist, was found submerged in the bathtub of her Salt Lake City, Utah, home by her then-boyfriend, Nils Abramson. "The door was unlocked," Abramson says. "I could hear the water running." She was dead.
"It's not a suicide," Abramson tells Spencer. "I mean, it just can't be."
It took six weeks for the autopsy report to be released, which listed the cause of death as drowning. The manner of her death was listed as "undetermined," leaving open the possibility of suicide.
However, friends say there were long-standing issues between Von Schwedler and her ex-husband, Wall, a leading pediatrician, that existed long after their 2006 divorce.
"He blamed Uta for everything that went wrong in his life," says family friend Klaus Fiebig. "It was, it was bizarre." Yet, one time, Fiebig continues, "he asked me, 'Would it be bad if Uta wasn't around anymore?"
Simply asking the question, though, does not prove someone guilty. And evidence at the scene of Von Schwedler's death suggested she might really have killed herself.
Pelle Wall was also concerned about his three younger siblings, who like him lived with his father at the time of Von Schwedler's death. "I really didn't feel safe," he says. "This was not a superficial concern. This was I might die."
Wall's sister, Wendy Wall, says her brother is innocent. "There's no doubt in my mind that Johnny did not kill Uta," Wall says. "He cared too much about having his kids' mother in his kids' lives."
Wendy Wall says everyone in her family still loves Pelle. "I think that Johnny felt devastated when, you know, when Pelle – in some ways you could say turned against him," she says. "Pelle's a teenager," she adds. "He got swept up in a crusade that was started by others."
Pelle Wall won't give up.
"I'm not sure how many people would have the courage and conviction of character to do what he's done," says family friend Amy Oglesby.