True-crime TV has been having a moment for the past few years, and popularity for the genre is showing no sign of slowing down.

There's been a lot of commentary around issues of bias when it comes to documenting real criminal events, particularly when a case seems unresolved. But there are also instances when the filming of events, and the increased public interest these shows bring, actually help the cases in question along.

1. Making A Murderer

Netflix

Ten years in the making, this Netflix hit brought worldwide attention to the case of Teresa Halbach's murder and the conviction of Steven Avery and his nephew Brendan Dassey.

Whilst there have been questions surrounding the possible one-sided nature of the docuseries, with critics claiming that it favoured the defence argument, there's no denying that questions surrounding the fairness of the trial have turned out to be justified.

So much so that Avery found himself gaining a brand new lawyer off the back of the series – enter Kathleen Zellner, known for her work around exonerations. She has brought fresh eyes and a wealth of experience to the case and, one month after Making a Murderer's release, filed an appeal on behalf of Avery.

Zellner has also stated that she had the "world's best experts" looking into the idea that evidence had been planted – something that was explored in detail throughout the filmed trial. This motion was denied, but Zellner has made it clear that she will "never stop" in her efforts to win Avery's freedom. Most recently, her work on the case has brought new names into the mix when it comes to suspects.

MORRY GASH / AP/Press Association Images PA Images

Meanwhile, the widespread uproar surrounding Brendan Dassey's confession, which aired during MaM series one, further spurred on appeals against his verdict. Brendan's conviction was overturned by a federal judge, on the grounds that his confession was "involuntary", but after a series of appeals by both sides it was eventually ruled that Dassey's life sentence would remain in effect.

This is all expected to be covered in series two of Making a Murderer, due to land on Netflix at some point this year, and it remains to be seen what influence this might have.

2. The Staircase

Netflix

The 13-part docu-series hit Netflix earlier this year, merging the 2004 original and the 2013 follow-up with three all-new episodes. Whilst many viewers have been left divided on Michael Peterson's innocence, the new instalments pushed the investigation further and did offer a resolution – at least in the eyes of the law.

Having spent a number of years behind bars following his conviction for the murder of his with Kathleen Peterson, Michael found himself in front of the judge once again when crucial evidence that was used against him was called into question.

He ultimately ended up taking an 'Alford plea' in order to avoid another lengthy trial and possible conviction. In layman's terms, this means that he does not admit guilt, but still pleaded guilty in the acknowledgement that the evidence is substantial enough for a conviction (whatever the truth may be).

Although these events would have transpired with or without the documentary cameras, old footage from Peterson's original trial – and the '04 documentary – were played back in the courtroom. This helped defense lawyer David Rudolf make his case against blood-spatter analyst Duane Deever, whose practices had been called into question through a different murder case, all assisting Peterson's plea deal.

3. Serial

Karl Merton Ferron/Baltimore Sun ELLEMEN

Okay, a podcast not a TV show. A spin-off of This American Life, it looked into the 1999 murder of Hae Min Lee and attempted to shed more light on whether or not her high school boyfriend Adnan Syed, who had been convicted of the crime, was indeed guilty.

Hosted by journalist Sarah Koenig, the audio episodes revisited key evidence in the case and also conducted new interviews with some of the key players.

The 23-part series gained a lot of popularity, sparking fresh interest in the case and spurring on a new appeal from Syed's legal team. He has since had his conviction overturned and has been granted a new trial, but will need to wait in prison for the outcome of the State's appeal (which seeks to reinstate his original sentence) after Maryland's highest court agreed to hear it.

The whole process is still ongoing and Rabia O'Chaudry – author of Adnan's Story and co-host of the Undisclosed podcast, which looks at the case in even more detail – sharing regular updates via Twitter.

4. The Jinx

HBO

There are so many things to say about this six-part HBO documentary series, which delved into the mysterious – and murky – circumstances surrounding multimillionaire Robert Durst.

What with his lightless eyes, the confrontation over those handwritten letters and THE BURP, we're shuddering just thinking about it all.

Each twist and turn was met with a gasp, but one thing that filmmaker Andrew Jarecki probably didn't count on was getting a recorded confession of the crimes he'd spent the series speculating about. What a climax.

Long suspected of foul play, many have argued that, without his involvement in the series, Durst would not be standing trial today. Even though the recorded admission – which he has previously claimed came under the influence of drugs – was the standout moment of the series, he was actually arrested by FBI agents one day before the final episode of The Jinx aired.

According to Deadline, prosecutors feared that he might flee if he realised the weight of the evidence that had been presented in the documentary. Rolling Stone reported that analysis of the letters put before him during the series proved to be crucial in his arrest.

5. Bullseye

Okay, so this one isn't technically a true-crime documentary (obviously!) but when a prime time game show helps to identify and capture a serial killer, that's worth a mention right?

John William Cooper had evaded capture for years, but had long been suspected of the murders of four people – a brother and sister in 1985 and a couple in 1989.

When his on-screen appearance was compared to an artist's impression of the suspect, the police felt that they finally had their man. It wasn't just the likeness to the drawing, but he also happened to mention the area in which the '89 murders had taken place.

The footage from his time on the show, which was filmed one month before the '89 killings, ended up being a crucial piece of evidence.

"There was Cooper, just a month before the killings, revealing on national television knowledge of the area where the Dixons would be murdered," now-retired chief superintendent Steve Wilkins said.

A number of crime documentaries have since been made around this case, with the most recent one, entitled 'The Gameshow Serial Killer: Police Tapes', airing on ITV earlier this year.

While we're on non-documentaries getting involved in crimes, an episode of Curb Your Enthusiasm provided an alibi for a suspect in a murder case. The documentary Long Shot describes how Juan Catalan was at a Dodgers game in LA on the night of the murder he was accused of, and that the only evidence of his presence in the stadium was an episode of Curb, filmed that evening at Dodgers Stadium. Phew!

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