After the 2005 murder of Teresa Halbach, Tom Fassbender, co-lead investigator on the case, conducted multiple interviews with 16-year-old Brendan Dassey to see what information he may have known about the Wisconsin photographer’s death. Dassey, nephew of Steven Avery, who quickly became a suspect in the murder and whose story was told in the Netflix documentary series Making a Murderer, told authorities he was with his uncle the night Halbach disappeared.

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After the docuseries aired, many felt that Dassey, who revealed supposed details of the murder to Fassbender during an interrogation, was treated unfairly and coerced into confessing to the crime.

WATCH: Former Prosecutor Featured In ‘Making A Murderer’: ‘I’m Here To Set The Record Straight’

On Monday’s episode of Dr. Phil, Fassbender says in no way did he coerce Dassey, and that the teen voluntarily offered up details about the murder.

“When Brendan disclosed his involvement in Teresa’s murder on March 1, both investigator Weger and I were taken aback," Fassbender says in the video above. "The first time we interviewed Brendan Dassey on November 6, he was asked about a fire and said there was no fire that week. Then, on November 10, he did admit that there was a fire and that he helped Steven tend to the fire. Then, going on to February 27, he admitted to seeing parts of Teresa in that fire."

Fassbender says with Dassey’s information, they were able to complete a search warrant of Avery’s property.

“During a search of that garage, we found two bullet fragments. One of those fragments we found to forensically match the 22 caliber rifle that Steven used and was found above his headboard in his bedroom,” Fassbender says. “That same bullet fragment was found to have Teresa’s DNA on it. There’s no planted evidence nor coercion in this case.”

WATCH: Why Defense Attorney Featured in 'Making a Murderer' Says He Believes Police Planted Evidence Against Steven Avery

Avery and Dassey were convicted of Halbach’s murder, although both maintain their innocence. Avery is currently serving life in prison without the possibility of parole at the Waupun Correctional Institution in Wisconsin. In August 2016, a federal magistrate overturned Dassey’s murder conviction finding that the teen's confession was unconstitutionally coerced by Fassbender and his partner. Yet, he is still in prison today as that ruling is being appealed.

On Monday’s episode, Fassbender and Ken Kratz, former district attorney of Calumet County, Wisconsin who tried Avery and Dassey, reveal more details about the case that they say were omitted from the documentary series. And, hear from Avery’s former attorney Jerry Buting and why he says he believes evidence was planted and Avery is innocent. Check here to see where you can watch.

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