A lawyer representing convicted killer Steven Avery said advances in forensic testing could help exonerate her client, who is serving life in prison for the 2005 murder of Teresa Halbach.

The 53-year-old murderer gained national attention following the release of the popular Netflix documentary series "Making a Murderer," which explores his case from his perspective, in late 2015.

During an interview with NBC's Dateline, Avery's attorney, Kathleen Zellner, said new data collected and tested through advanced technology proves Avery is innocent.

"Generally, since 2007, there have been significant advances in forensic testing ... the clearest way to do this is with scientific testing," said Zellner in her first TV interview since taking the case, reports NBC News. "There was a lot of evidence that wasn't tested."

Zellner, who specializes in wrongful convictions cases, also argues that there may be other suspects in the case. Meanwhile, Halbach claims that he was framed by local law enforcement officials in Halbach's klling.

Before the Halbach's murder, Avery served 18 years in prison for raping a jogger in Manitowoc County. He was then exonerated by DNA evidence and released in 2003. After his release, he filed a $36 million federal lawsuit against Manitowoc County and its former sheriff and district attorney over their handling of his wrongful conviction.

However, while the civil suit was underway, Halbach was raped, murdered and mutilated in Oct. 2005, reports The Wisconsin Journal. Evidence suggested that Avery was the culprit in the 25-year-old freelance photographer's slaying, and he was subsequently arrested and convicted. His 16-year-old nephew Brendan Dassey also received a life sentence after giving a four-hour long confession about how he took part in the rape.

Nevertheless, Avery has maintained his innocence, arguing that he was framed by the Manitowoc County Sheriff's Department. According to Avery's former attorneys, physical evidence implicating him in the crime could have been planted by the sheriff's department in retaliation for the multi-million dollar lawsuit he filed against them. His lawyer also said Dassey, who has a low IQ, was coaxed by police into giving a false confession, which doesn't even match evidence in the murder.

"From the evidence I've looked at I think he is innocent," said Jerry Buting, a lawyer for Avery in the Halbach case, to Dateline. "I think he certainly was not guilty beyond a reasonable doubt under the evidence that was presented."

However, Ken Kratz, the former district attorney in Calumet County, Wisconsin who prosecuted Avery and Dassey, said "Steven Avery's guilty and deserves to be right where he is."

Kratz added, "With any one of these facts, you can come up with a 'what-if' scenario. But at some point this conspiracy theory collapses under its own weight."

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