Man gets 9 years for killing, burning co-star in porn films shot at Richardson office

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  A jury on Friday sentenced a 20-year-old man to nine years in prison for murdering a Richardson pornographer who was pummeled more than 30 times with a hammer after a game of "doctor" went too far.
  
  Trying to spare Daeveion Mangum a life sentence, the defense argued that he killed Michael Castagne, before setting fire to his office, in a fit of "sudden passion."
  
  Attorney Stephen Duplantis said the 60-year-old filmmaker was grooming the much younger Mangum as a sexual predator would a child.
  
  "He was trying to provide [for his family], but he seeked the wrong way," said Kizzie Sanders, Mangum's mother. "There are people out there who will try to hurt you no matter how old you are."
  
  Prosecutor Trey Stock dismissed that argument.
  
  "This was not a 7-year-old with candy," he said. "This is a 20-year-old man with a wife and kids he kept in the dark."
  
  The wife, Dashunna Mangum, pleaded with jurors to go easy on her husband in doling out his punishment.
  
  "Think of my kids and me," she said. "I have to tell my kids he's not going to be here."
  
  On Wednesday, Mangum took the stand in his own defense to admit he killed Castagne, his co-star in a series of pornographic movies.
  
  "I was thinking that's what it takes to be a porn star," Mangum testified Wednesday, saying he acted in self-defense.
  
  Police were dispatched to the 500 block of East Arapaho Road after the fire department received a call about smoke coming from the office. Inside, firefighters found the 60-year-old's body draped in smoldering plastic.
  
  A man who had been there earlier in the day later told police he had seen Mangum arguing with Castagne before he left. Police arrested Mangum on traffic warrants, and he confessed to killing Castagne.
  
  In closing arguments Thursday, the defense said Mangum was trying to protect himself and that it was Castagne who brought the hammer into the room and threatened to strike Mangum with it.
  
  "Would we even be here if this were a 19-year-old girl and a 60-year-old man?" Duplantis asked the jury Thursday.
  
  But prosecutors said the fact that Mangum burned the office shows he understood the enormity of the crime.
  
  Mangum said in court that he and Castagne had an argument over what he was willing to do on film. When Castagne confronted him wearing only his boxers and asked if he was ready, Mangum replied, "I want to go home."
  
  As the victim described what they were going to do, Mangum says, he picked up a hammer and began hitting Castagne in the heat of the moment. After the second blow, Castagne fell to the floor.
  
  Mangum said he kept hitting the man, more than 30 times, "because my life was in danger."
  
  
  Before that night, the two men had worked on at least three pornographic films together, the prosecution said Wednesday. In one film, Castagne played the role of a doctor and gave Mangum a prostate exam.
  
  When the prosecution asked Mangum whether he remembered the interaction, he said it would not have surprised him. He also told prosecutors he believed Castagne to be a licensed medical doctor, a role he said he frequently played.
  
  "While I am not a doctor,” reads an excerpt from Castagne's website posted between 2009 and 2013, "I have enjoyed 'playing doctor' since I was a young boy.”
  
  Of the “models” Castagne used in his films, the website says, "Most of them fell right into the routine of doctor and patient, because it was so natural for them to do so. ... Many of them told me, after their exam video was recorded, that my exam demonstration was far more detailed than their own doctor had given to them."
  
  Castagne had a criminal record: In 1990, he was convicted on a charge of sexual performance by a child from an incident five years earlier.