Manitowoc County Sheriff Robert Hermann is standing by his department's investigation into the case of Steven Avery, a man accused of gruesomely murdering photographer Teresa Halbach.

The case gained national attention following the Netflix (NFLX) documentary series "Making a Murderer," which documented the trial closely for years.

"I don't believe that this is a documentary because it leaves out a lot of information," Hermann told CNNMoney.

Pieces of evidence Hermann referenced: Avery's DNA found under the hood latch of Halbach's vehicle and leg irons and handcuffs found in the residence.

The filmmakers told CNNMoney they picked the most crucial evidence for the film and refute being called biased.

"We did not have a horse in this race," filmmaker Laura Ricciardi said. "It was no consequence to us if Steven Avery was found guilty or not guilty."

Related: Filmmakers say juror believed Avery was not guilty

The series raises the question: Was Steven Avery was framed?

Prior to his conviction, Avery had been falsely accused of rape and served 18 years in prison. He was exonerated in 2003 and was pursuing a multi-million dollar lawsuit against Manitowoc county and its sheriff when he was accused of murdering Halbach. Avery's defense made the case that officers investigating Avery had a conflict of interest and stayed involved after they were ordered to hand over the investigation to a neighboring county.

"We were never ordered to stay out of the investigation." Hermann refuted. "At no time did I say we would not be involved or assist. I asked them to take the lead."

When key pieces of evidence were found by Manitowoc officers involved in Avery's first case, the defense implied the evidence could have been planted.

One crucial scene in the documentary implies one of the Manitowoc officers who had previous involvement in Avery's first case may have discovered Halbach's vehicle before it was reported days later. The defense played a tape at the trial in which the officer calls in a license plate number and names the car type, leaving viewers wondering: was he standing in front of the car, and if so, why was it reported found on Avery's property days later?

Hermann strongly refutes the implication.

"He did not have the vehicle in front of him. He had a plate number that was given to him by the Calumet County Sheriff's office," he told CNNMoney.

Why did the officer also have the car type?

"That's common practice, to run the plate and have that information on a teletype. A lot of times, it's attached to a report if there's a report on it," Hermann said. "The other thing is that Calumet county ... also knew that one of her last stops was in Manitowoc county."

The documentary has spurred hundreds of thousands of people to sign petitions in support of Steven Avery, calling on the conviction to be overturned.

Hermann has a different take.

"I believe that justice was served and he was convicted and is guilty," he said. "Are there mistakes made during investigations? Not a question. I think overall, it was handled very well."