Netflix’s gripping true crime series “Making a Murderer” explores the complex case of Steven Avery, a Wisconsin man who was wrongfully convicted of sexual assault and eventually exonerated ― only to be convicted of murder years later under suspicious circumstances. The 10-part documentary illuminates deep flaws in the U.S. criminal justice system by putting on display a panoply of questionable behavior from police and prosecutors. While the series’ revelations may be shocking to some, the truth is they’re all too common.

Avery spent 18 years in prison after being wrongfully convicted of sexual assault and attempted murder in 1985. In 2003, improved DNA testing technology revealed that the actual assailant was Gregory Allen, a convicted rapist who was already serving a 60-year prison sentence for another crime. Avery was set free and began to get his life back on track. He filed a $36 million federal lawsuit against the county, the sheriff and the district attorney in his case, alleging that they were negligent in their investigation and prosecution. Avery’s case became known in Wisconsin as an example of overzealous policing, and it prompted state lawmakers to pass a bill in Avery’s name intended to halt wrongful convictions.

Two years later, Avery found himself at the center of another crime ― the gruesome death of Teresa Halbach, a freelance photographer whose remains were found in a burn pit on Avery’s property.

Avery was arrested and convicted in the killing of Halbach, and was sentenced for the crime alongside his young nephew, who was charged as an accomplice. But in “Making a Murderer,” the filmmakers showcase compelling evidence suggesting that Avery may have been framed for Halbach’s murder by the same law enforcement officials who wrongfully accused him of sexual assault in 1985.

Along the way, the filmmakers examine, explain or at least allude to any number of dubious techniques that police and prosecutors have been known to use ― techniques that critics say distort the criminal justice system and prevent people all over the country from getting a fair shake.

Coaxing ‘Confessions’ Out Of Innocent People

Police obtained what they said was a confession from Brendan Dassey, Avery’s nephew, that formed the basis for much of the prosecution’s case against Avery. At one point in the documentary, Ken Kratz, the prosecutor in the Halbach murder case, describes a supposed timeline of the murder in upsetting detail, and it’s implied that much of the information in that timeline came from Dassey’s detailed account. But when you watch the tape of the actual police interview with Dassey, it looks less like a detailed confession and much more like coercion.

At the time of the interview, Dassey was 16 and did not have an attorney or a parent present. According to court records, Dassey has an IQ of somewhere between 69 and 73 ― an IQ of 70 is often considered the threshold for intellectual disability ― and on the tape, you can see police posing detailed questions to Dassey, who replies with short, often one-word answers.

This is a well-known and controversial style of interrogation. It’s called the Reid technique, and it’s led to numerous situations where an innocent person ends up confessing to a crime they never committed. Teens are especially susceptible to tactics like this.

“In a nutshell, the primal fatal flaw of the Reid technique, on display in the interrogation of Brendan Dassey, is that it is a guilt-presumptive process inflicted on suspects who have already been judged deceptive and guilty,” Saul Kassin, a psychology professor at the John Jay College of Criminal Justice, told The Huffington Post in an email. “That is why the interrogation of Dassey appeared so relentlessly driven to produce a confession ― regardless of all his denials, regardless of his innocence claims, and regardless of his ignorance ― until prompted ― of basic crime facts that a perpetrator should have known.”

In an analysis of hundreds of cases going back to 1989, false confessions were found to be one of the leading causes of wrongful convictions, according to the Innocence Project, a nonprofit legal clinic dedicated to exonerating people who have been wrongfully convicted. Overall, about 31 percent of wrongful conviction cases included a false confession, but for homicide cases alone, that number balloons to 63 percent. More than 30 exonerees who were later freed due to DNA evidence pled guilty to crimes they did not commit.

“The Reid technique is perfectly effective when used on suspects who are guilty,” Kassin said. “The problem is, it is overly effective, on those [who] are innocent too. And there’s why you get false confessions.”

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The ‘Hidden Crime’ Of Evidence Planting

One of the most shocking allegations in the Halbach case is the notion put forward by the defense team, attorneys Dean Strang and Jerry Buting, that police may have planted evidence in order to secure a conviction of Avery, as retaliation for Avery’s lawsuit against the parties who wrongfully convicted him in 1985. Throughout “Making a Murderer,” police and prosecutors vehemently deny this charge. Ultimately, the documentary doesn’t establish one way or another whether it happened.

Unlike many other types of crime, there’s little data available about evidence planting. There have been widely publicized cases of cops being busted for planting evidence to secure an arrest or conviction, but on a national scale, it’s hard to build up a picture of how, why, where or when it happens.

“We really don’t know how common the problem of planting evidence or tampering with evidence is in police departments in the United States,” Philip Stinson, a former police officer and professor at Bowling Green State University’s criminal justice program, told HuffPost. “It is a hidden crime.”

Stinson said he’s noticed some patterns in cases where cops are charged with planting evidence. Most of the cases are in some way drug-related, he said, and “some of the cases are seemingly motivated by revenge.”

According to a report by the National Registry of Exonerations, there were at least 1,100 cases between 1989 and 2012, involving individuals convicted of a crime and later exonerated, that involved police corruption. The report notes that officers in these cases “systematically framed innocent defendants for non-existent crimes, mostly possession of illegal drugs or guns.”

“There are countless documented cases where innocent people have spent decades behind bars because the police manipulated or concealed evidence,” U.S. Circuit Judge Alex Kozinski wrote last year in a paper critiquing the criminal justice system.

Kozinski wrote that there’s a “bedrock assumption” underlying the U.S. criminal justice process ― namely, the assumption that police are objective in their investigations. But even when the police operate ethically, he wrote, the vast discretion they’re afforded ― in terms of which “leads to pursue, which witnesses to interview, what forensic tests to conduct” and so on ― greatly influence the course of an investigation and trial.

Cops are in a unique position to “manufacture or destroy evidence, influence witnesses [and] extract confessions” if they choose, Kozinski wrote. In this way, they have the opportunity to “direct the investigation so as to stack the deck against people they believe should be convicted.”

But such cases of planted evidence, Kozinski told HuffPost in an interview, “are either extremely rare or extremely difficult to detect ― probably both.”

‘Law Enforcement Agencies Are Territorial’

The Manitowoc County Sheriff’s Office was the lead law enforcement agency involved in Avery’s sexual assault case in the 1980s. For that wrongful conviction, which cost him 18 years in prison, Avery went on to pursue damages via a multimillion-dollar lawsuit against the county and its former sheriff, Thomas Kocourek ― a lawsuit that was in progress when law enforcement began investigating Avery for Halbach’s murder.

The Calumet County sheriffs were the lead investigators in the Halbach case, but Manitowoc officers ― some of whom were explicitly linked to Avery’s wrongful conviction for sexual assault, and had been deposed for his subsequent lawsuit against the county ― were involved in parts of the investigation at his residence.

During the Halbach case, prosecutors argued that the Manitowoc officers were nearly always accompanied and supervised by police from Calumet County. But it wasn’t an airtight system, and it certainly opened the door to questions. For example, after Calumet authorities had searched for days for the key to Halbach’s car ― a crucial piece of evidence linking Avery to Halbach ― it was a member of the Manitowoc County Sheriff’s Office who found the key inside Avery’s trailer. This might just have been coincidence, of course, but to the defense it seemed suspicious.

At the very least, the involvement of Manitowoc authorities in the Halbach case seems like a pretty clear conflict of interest. So how could an agency already charged with botching a previous investigation of the same man remain a part of a new investigation? Stinson says it’s politics as usual for police.

“The decision as to which agency is going to investigate a crime is sometimes a political one, although it is always clear which agency has primary jurisdiction,” Stinson said. “But law enforcement agencies are territorial, and often police chiefs don’t want to lose control of an investigation, and similarly, local prosecutors don’t like having to let an outside agency take over.”

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'Some Fields.. Are Built On Nothing But Guesswork'

DNA testing ultimately set Avery free from prison in the sexual assault case. But during his murder trial a couple of years later, Avery's defense argued that the FBI had acted with such haste in its testing for the Halbach case that the results weren't reliable. "Making a Murderer" goes on to offer additional reasons to think Avery's prosecution may have involved improper forensic science -- which, according to the Innocence Project, is one of the leading causes of wrongful conviction.

“Too often, forensic analysts’ testimony goes further than the science allows,” research from the Innocence Project reads. “Many forensic techniques that have been practiced for years -- without the benefit of sufficient scientific research -- are accepted and repeated as fact. Juries are left with the impression that the evidence is more scientific than it is, and the potential for wrongful convictions increases.”

The nonprofit points out that while the vast majority of forensic scientists are ethical and responsible, mistakes do still occur. Take the FBI’s admission that from 1972 through 1999, almost every single examiner in the bureau's elite forensics unit gave flawed testimony in nearly every trial in which they presented evidence against defendants.

The problems with forensic science go beyond bloodwork and DNA. Other fields of expertise, like those of ballistics, bloodstain pattern identification and foot and tire print analysis, have been “long accepted by the courts as largely infallible,” Kozinksi wrote in his 2015 paper. But, he argued, those techniques should be viewed with considerable skepticism.

“Some fields of forensic expertise are built on nothing but guesswork and false common sense,” Kozkinski wrote. “Many defendants have been convicted and spent countless years in prison based on evidence by arson experts who were later shown to be little better than witch doctors.”

Sometimes People Are Convicted Of Crimes They Didn’t Commit

Justice Antonin Scalia famously said in a 2007 opinion that American criminal convictions have an error rate of just 0.027 percent -- "or, to put it another way, a success rate of 99.973 percent." However, research on the subject suggests the true error rate is significantly higher.

It’s not entirely clear how many innocent people have been wrongfully convicted, but the Innocence Project, citing multiple studies, estimates that as many as 2.3 percent to 5 percent of all U.S. prisoners may be innocent. In fact, it may be even more than that. The United States leads the world in incarceration of its own citizens, and with approximately 2 million Americans currently locked away, even a wrongful conviction rate of 1 percent translates to 20,000 people behind bars for crimes they didn't commit.

And of all U.S. prisoners sentenced to death, about 1 in 25 are likely innocent, according to another recent study. About 1.6 percent of individuals on death row are ultimately exonerated, but the researchers say that if all defendants on death row were allowed to remain there indefinitely, at least 4.1 percent would eventually be exonerated -- a figure the researchers call "a conservative estimate."

Tunnel Vision: 'A Recipe For Disaster'

During the course of "Making a Murderer," it’s revealed that Manitowoc authorities had evidence that there may have been another suspect in Avery’s sexual assault case. For years, though, no report was filed about that evidence. Avery’s defense argues that law enforcement, in both Avery’s sexual assault case and his murder case, simply decided he was guilty before they had the evidence to prove it. The cops and prosecutors deny they had anything against Avery, maintaining that the evidence led them to him.

Daniel Medwed, a law professor at Northeastern University who has studied this phenomenon in depth, told HuffPost that police and prosecutors have been known to lock on to a theory and “neglect countervailing evidence” if they decide a certain individual must be guilty.

“Psychologists call this ‘confirmation bias,’” Medwed said. “After you develop a hypothesis, you see everything through that lens and interpret data in a way that confirms that view."

Kozinski echoed similar sentiments to HuffPost, saying that when police are convinced of a person's guilt, this kind of “tunnel vision” is “probably the number one cause of wrongful convictions.”

This month, The Police Chief, the magazine of the International Association of Chiefs of Police, published an extensive report describing how “tunnel vision” can lead to overturned convictions.

“This heuristic is particularly ill-suited to solving complex, dynamic investigations,” writes Dr. Kim Rossmo, a university chair and former detective inspector. “Focusing on the first likely suspect, then closing the investigation off to alternative theories is a recipe for disaster.”

Sentences 'So Excessively Severe, They Take Your Breath Away'

At one point in "Making a Murderer," Dassey's family becomes concerned that the boy's attorney is interested in persuading him to sign a plea deal -- one that would likely assert Dassey’s guilt, but would also allow him to serve less time in prison.

It's still not clear whether Dassey was an innocent teen coaxed into taking on responsibility for a horrible crime or whether he did, in fact, participate in the killing like police say he did. But what we do know is that he ultimately didn't take the deal -- and that his experience reflects a not-uncommon temptation for criminal defendants to enter into plea bargains out of fear of harsh sentences. Sometimes, defendants will do this even when they're actually innocent.

“The question of how many innocent people [plead] guilty is crucial, and likely the iceberg beneath the surface,” Medwed told HuffPost in an email. “Because people are offered a good ‘deal’ to plead out there is reason to believe a rational, risk-averse innocent defendant worried about blowing trial would take the plea.”

Plea bargains aren't always bad. In fact, they can be an effective and efficient tool to resolve cases. But according to a 2013 Human Rights Watch study, the U.S. plea bargaining system often creates situations where a federal prosecutor will "strong-arm" a defendant -- offering them a shorter prison term if they plead guilty and threatening them with sentences that can be “so excessively severe, they take your breath away,” in the words of Judge John Gleeson of the Eastern District of New York.

No criminal justice system in the world is perfect. But it's hard to watch "Making a Murderer" -- or simply pay attention to the news for any length of time -- and not come away with the idea that the U.S. could be doing much, much better.