Making a Murderer's Steven Avery's mum Dolores has died

<i>Making a Murderer: Part 2</i> picks up the story of Steven Avery (Netflix)
Steven Avery was the subject of Making a Murderer. (Netflix)

Dolores Avery, the mum of Steven Avery who is featured in hit Netflix documentary Making a Murderer, has died aged 83.

Steven became well known through the 2015 documentary which looked at his imprisonment for the murder of photographer Teresa Halbach, 25, in 2007.

Read more: Making a Murderer part 2 gathers new evidence

His nephew Brendan Dassey was also convicted and jailed, but both men insist they are innocent and have been working to get a retrial, with Dolores one of their biggest supporters.

She appeared many times in the series as she campaigned to free her son.

Key art for 'Making A Murderer: Part 2' (Netflix)
Making A Murderer ran for two series. (Netflix)

Kathleen Zellner, Steven's attorney, announced the sad news to her Twitter followers on Thursday morning, saying it tragically happened the day before Steven's 59th birthday.

She tweeted: "Update: Fate dealt another cruel blow to Steven Avery today right before his birthday tomorrow; his mother Dolores Avery passed away at 6:50 am.

"He needs your support now more than ever. RIP Ma Avery."

To view this content, you'll need to update your privacy settings.
Please click here to do so.

Earl, Steven's brother, told TMZ that their mother had been in a hospice and suffering from dementia.

Steven also told TMZ: "Losing my parents before I got out has always been my worst nightmare. Now it has happened.

"I worry my Dad will not live to see me as a free man. Today I lost the person I most wanted to take care of and give a better life when I am freed. I cannot put in words the pain of losing my mom."

Making A Murderer to get sequel series on Netflix
Brendan Dassey was also convicted. (Netflix)

He is currently serving life in prison for the murder, having previously served 18 years for being wrongly convicted of a sexual assault and attempted murder.

Attorney Zellner took on his case in 2016 and argues that evidence collected by police went beyond their search warrant remit, also saying that she has new witnesses which would justify a retrial.

Many Making a Murderer viewers became convinced that Avery and Dassey had been unfairly treated by police after seeing footage of their interrogations.

Watch: Governor rejects pardon request from documentary subject