If you don't believe Steven Avery is innocent maybe you will now when I till you the story of Cara Knott.
Cara Knott was murdered by a California Highway Patrol Officer in 1986. The officer denied the murder, and still does to this date.
As you know Steven Avery was eventually exonerated of the sexual assault and rape charge against him in 1985 when DNA analysis 18 years later was able to link the crime to another man.
On Cara Knott's shoe there was a spec of blood. Conclusive DNA testing was not available back in 1986, all they could do was obtain the blood type of the person that the blood belonged to. The blood belonged to somebody with the blood type AB negative, the rarest blood type. Coincidentally the patrol officer had that blood type.
In 2004, the officer was asked whether he would like to provide his DNA to help prove that the blood on the shoe was not his blood and to hopefully try and prove his innocence using DNA technology. He refused to provide his DNA. He also refused to answer why he would not provide his DNA. As a result he is still in jail and won't be eligible for parole until 2026 i believe.
This shows you the lengths that somebody (especially a police officer) is willing to go, to deny that they committed murder.