In his new tell-all about Making a Murderer’s infamous case, prosecutor Ken Kratz makes the shocking allegation that Brendan Dassey accused his killer uncle Steven Avery of sexual abuse.

“Brendan made those allegations against his uncle Steven on the phone to his mother,” the Avery: The Case Against Steven Avery and What Making a Murderer Gets Wrong author, 57, tells RadarOnline.com in an exclusive video interview. “He made them to law enforcement officers. He made those allegations several times, that’s why I included it.”

Kratz insists he didn’t include the claim to shock or horrify readers. Rather, he thought it was an important detail about the sick uncle/nephew duo’s complicated relationship. (As Radar readers and Making a Murderer fans know, Avery, 54, and Dassey, 27, were infamously convicted in the October 31, 2005 rape and murder of 25-year-old Teresa Halbach on the family’s Wisconsin property.)

“This was another way to keep Brendan quiet,” Kratz explains. “A way to buy his silence.”

“I believe his uncle involved or included Brendan in these crimes in part to keep him quiet. To keep him from telling what happened or what he saw. To involve somebody in a rape or a murder or in disposing of a human body is a pretty strong way to keep somebody silent.”

Avery is accused of kidnapping Halbach, and then encouraging the then 16-year-old special needs high school student to join in on his heinous crimes.

Two years later, both men were sentenced to life in prison.

Kratz also claims in his book that Avery was accused of raping a teen niece in the summer of 2004, and sexually assaulting a young babysitter in the 1980’s. Neither detail was included in the Netflix hit show.

While Avery’s new attorney is planning a new appeal in the decade-old case, Dassey’s conviction was overturned in August 2016. He will remain incarcerated pending an appeal.

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