The second season of Making a Murderer will drop on Netflix on October 19.

When the first season premiered in December 2015, it became an instant phenomenon. For weeks all people wanted to talk about was the once little-known murder trial from Manitowoc County, Wisconsin.

The first instalment of the true crime doco-series looked at the case of Steven Avery – a man who was wrongly convicted and exonerated for rape, and then later convicted for the murder of 25-year-old photographer, Teresa Halbach.

Avery’s teenage nephew, Brendan Dassey, was also convicted for his alleged role in the crime.

Watch the trailer for season two…

The first season generated a huge amount of debate around whether Avery was actually guilty or once again wrongly convicted. Most viewers sat firmly on either side of the debate.

After the series aired, both Avery and Dassey launched appeals.

In 2016, a judge ruled that Dassey should be released from prison. But then another judge ruled that he should remain in prison.

In 2017, a Wisconsin judge denied Avery a new trial.

This new season will focus on what life has been like for Avery and Dassey behind bars for the past 11 years, and the emotional toll the appeals process has had on the two convicted murderers.

Here’s everything you need to know from the first season, before you delve into the second:

Who is Steven Avery?

Steven Avery was born in 1962 to parents Allan and Dolores Avery. He grew up on the family’s 40-acre salvage yard in Manitowoc County, Wisconsin.

He only has an IQ of 70.

The Avery family was well-known and disliked in the local community. Avery had admitted to various crimes in the past and had even pleaded guilty to animal cruelty after he threw the family’s car onto a bonfire.

The wrongful conviction.

In 1985, Avery was arrested for the rape and assault of a woman named Penny Beerntsen.

Beerntsen was attacked while jogging alongside Lake Michigan and later identified Avery in a police line-up.

Avery was found guilty of the crime and was sentenced to 32 years in jail. He served 18 years before he was ultimately found not guilty and released from prison in 2003.

DNA advances had allowed investigators to find the real culprit – a man named Gregory Allen who looked remarkably similar to Avery.

At the time of his conviction, Avery was married to a woman named Lori Mathiesen and the couple had four children together – Rachel, Jenny, and twins Steven and William.

Lori filed for divorce in 1998 while Avery was still in prison.

The lawsuit.

After Avery was released, Wisconsin’s Department of Justice found no wrongdoing on the part of Manitowoc County’s police department when it came to his wrongful conviction.

Avery then filed a $36 million lawsuit against the county, former sheriff Tom Kocourek, and former district attorney Denis Vogel.

Why was Making a Murderer made?

Filmmakers Laura Ricciardi and Moira Demos had an agenda when they set out to make the docu-series.

They were very much embedded in Avery’s camp and wanted to tell the story from his perspective and his perspective only.

So obviously, it wasn’t a very well-balanced approach to the case. You need to keep that in mind while you watch season two.

Who was Teresa Halbach?

Teresa Halbach was a 25-year-old freelance photographer. She regularly took photos of cars to be listed in Auto Trader magazine.

On October 31, 2005, the day of her murder, Halbach was taking photos of a mini-van on Avery's property.

Four days later on November 3, Halbach's mother reported her missing. Remnants of her bones and teeth were found in a burn pit on Avery's property.

Her car was also later found on the property.

Avery's lawyers.

Avery's lawyers, Dean Strang and Jerry Buting, argued that police had set him up in retaliation for the lawsuit.

When the series dropped on Netflix, Strang became an immediate and, erm, unexpected sex symbol.

What every man should be like... Taking a few pages from your book mate! #DeanStrang pic.twitter.com/U2BJy2IbmX

— Ryan Cooper (@fryRyCooper) January 16, 2016

The blood in Halbach's car.

A lot of the first season focused on whether the Manitowoc County Sheriff’s Department tried to frame Avery as retaliation for the lawsuit.

Much of the season focused on the theory that a Manitowoc investigator planted Avery's blood - from a vial - in Halbach's car.

However, one of the FBI's DNA experts testified that the blood almost certainly came from Avery bleeding - and not from a vial.

Halbach's car keys.

The documentary also raised questions over the fact the key to Halbach's car was found in Avery's trailer.

A Manitowoc County investigator found it during the seventh search of the room.

However, the State Crime Laboratory chief testified that she found Avery's DNA on the key - which meant both the key and the DNA must have been planted for this theory to hold up.

Brendan Dassey.

In season one we saw how unfairly Brendan Dassey was treated by the legal system.

According to the filmmakers the 16-year-old, who had no criminal history and was in special education classes, was coached into confessing to the crime.

His first lawyer induced a confession out of him and then the prosecutor’s investigators repeatedly pressed Dassey for details about the crime until he told them what they wanted to hear.

However, the documentary never proved that Dassey was innocent of the crime.

You can stream Making A Murderer season two on Netflix from Friday October 19.