Steven Avery just wrote a letter from jail to all his 'Making a Murderer' supporters

Steven Avery wrote a letter from prison to his supporters over the weekend. And although it's short, it details the next step of his plan to be exonerated for murder.

His new attorney, Kathleen Zellner, shared the letter via Twitter. Dated January 29, it reads:

"To my supporters:

I want every forensic test possible done [because] I am innocent.

Steven Avery"

 Avery's request mirrors what Zellner said in a Dateline NBC special on Friday. She believes that advances in forensic testing will be the key to clearing his name. 

"Generally, since 2007, there have been significant advances in forensic testing ... the clearest way to do this is with scientific testing," Zellner said in her first TV interview since taking the case. "Am I going to tell you exactly what it is? I am not. But it's been a long time. There was a lot of evidence that wasn't tested."

Zellner, an Illinois lawyer who specializes in wrongful conviction cases, believes Avery is innocent of the 2005 murder of Halbach.

Activity around Avery's conviction for the murder of Teresa Halbach, an AutoTrader magazine photographer allegedly last seen on his property, has been noticeably higher over the past week.

On Friday, Avery's supporters protested in front of the courthouse in his home of Manitowoc County. That was followed by TV specials from "Dateline" and Investigation Discovery over the weekend.

Debates have been raging around Avery's conviction since December, when Netflix released "Making a Murderer," a 10-episode series following Avery and his then-teen nephew Brendan Dassey's trials in the murder of Halbach. Its themes of police corruption and the impact of wealth and media on the criminal justice system hit home with many viewers.

Avery and Dassey are currently serving a life sentence.