"I may have killed him" former FBI agent tells 911 after attack on son-in-law with baseball bat

An Irish businessman is killed by his American au-pair-turned-wife and her father -- was it self-defense or murder?

In Jason's Name

In her first American television interview, the sister of an Irish businessman who was murdered in Winston-Salem, N.C., speaks out to "48 Hours" to defend his honor.  "In Jason's Name" airs Saturday at 10/9c on CBS.  

Jason Corbett was beaten to death with a brick paver and a baseball bat in 2015 by his American au-pair-turned-wife, Molly Corbett, and her father, former FBI agent Tom Martens. Corbett and Martens maintained they killed Jason Corbett in self-defense after he tried to strangle Molly. They claimed he was abusive to Molly for years and he had been threatening to kill Molly the night he died. Prosecutors said Corbett's death was murder.

Victim's sister fights to clear her brother's name in new "48 Hours"

Now, Tracey Lynch is trying to set the record straight on her slain brother. 

"They claimed it was self-defense," Lynch tells "48 Hours"' Maureen Maher.

"The Martens didn't just murder Jason," Lynch says. "They tried to destroy his character."

"Jason was an amazing human being," Lynch says.

Jason Corbett was a 30-year-old father of two in Ireland, who suddenly found himself a widower when his first wife died of an asthma attack. He then decided he needed help with the children and hired Molly Martens, originally from Knoxville, Tenn. Soon, their relationship turned romantic, and they were married. Shortly after, they moved to the United States.

That's where the story turns leading up to the fateful night of August 2, 2015.

"I may have killed him" former FBI agent tells 911 after attack on son-in-law

Tom Martens told a 911 dispatcher that his son-in-law got into fight with his daughter and he had to intervene. "He's bleeding all over, and I, I may have killed him," he said.

Molly also told police that Jason, then 39, was "screaming 'I'm going to kill you.'"

"I just couldn't process it," Lynch says of her brother's death. "It was that, you know, he was my best friend. We were just two of the closest people in the world to each other outside my husband and children."

Lynch tells Maher that before his death her brother said he was unhappy and wanted to move home to Ireland.

"He said she was acting strange," Lynch says of Molly Corbett. "He would open up and say they were having difficulties, and then he would change the subject."

Molly Corbett and Tom Martens were arrested and charged with killing Jason Corbett. They were convicted of second-degree murder in 2017 but have maintained their innocence. Earlier this year they sought to get their convictions overturned on appeal. The court has yet to rule.