Baltimore detectives have exhumed the body of a priest as part of the investigation into the unsolved murder of a nun whose 1969 killing is the subject of Netflix's latest true-crime series, threatening to spoil the entire documentary before it even airs.

Father Joseph Maskell was exhumed from a Baltimore cemetery on February 28.

Baltimore County homicide detectives took a sample of his DNA immediately to test it against evidence found near the body of Sister Cathy Cessnik.

Sister Cathy was found dead at a garbage dump in November 1969, two months after she vanished. Her murder has haunted the community for years and is the subject of the The Keepers: Who Killed Sister Cathy? which will launch on the streaming site on May 19.

Police expect a result on the DNA test by the end of next week and say it will be a 'huge breakthrough' if Maskell's sample matches the evidence found at the scene.

Sister Cathy taught English at Archbishop Keough High School and was a rumored confidante of girls who had been raped and abused by Maskell who died in 2001.

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Father Joseph Maskell was exhumed from his Baltimore grave on February 28 to have his DNA tested against evidence found next to Sister Cathy Cessnik's body in 1969. He died in 2001 without ever facing arrest for the nun's murder. They are both shown above in photographs from the 1960s

Friends of the nun say she was murdered by the priest because she knew too much about the twisted web of pedophiles operating within the church.

They say Maskell was protected by his friends in the police force and by officials who wanted to keep a lid on the city's rampant corruption and crime.

The Keepers features testimony from Sister Cathy's former students who say they were raped by Maskell and terrified into keeping quiet about it. A trailer for the series points the finger squarely in his direction for her killing.

Sister Cathy's murder is the subject of Netflix's latest addictive series The Keepers

Baltimore County police has neither welcomed the documentary nor scorned it.

Elise Armacost of Baltimore County Police insisted that the timing of the exhumation had nothing to do with it on Thursday despite the fact that Maskell's name has been thrown around for decades.

'Our detectives have been working on this case long before the documentary. As a result of the documentary it's gotten a lot of attention but this case has been quite active since before then,' Armacost told DailyMail.com on Thursday.

Detectives will not reveal what evidence they found at the crime scene but say it has been sufficiently preserved over the last 40 years to be tested.

'The team of detectives felt strongly that in the interest of no stone being left un-turned that it was a step that had to be taken.

'[They felt that] we could not solve this case without knowing whether Maskell's DNA matched that evidence.

'It may not. The results may come back and show that it may not but we felt we needed to test it.

'We have been hoping to solve this case for some time and we believe we still can.'

Sister Cathy had bee teaching at the school for years when she vanished suddenly while out shopping for an engagement present for her cousin in September 1969.

When her body was discovered months later, she had a hole in the back of her head.

Sister Cathy taught at Archbishop Keough High School in Baltimore where dozens of girls claim to have been raped by the priests that ran it in the 1960s and 1970s

Former students including Abbie Schaub (left) and Jean Wehner (right) say Sister Cathy knew about Maskell's abuse and that she was murdered to stop her from exposing it. They took part in the Netflix documentary in a bid to solve the cold case after 40 years

Her car was found unlocked and neatly parked several blocks from the apartment where she was living at the time but there were no other clues.

The killing haunted Baltimore for decades.

In the 1990s, several former students of the school where she taught came forward to allege they had been routinely sexually abused by Maskell and his friends.

They told of being sold to fellow priests for sex sessions which he would profit from and described how he told them the abuse was in the name of God.

They won a settlement from the Archdiocese of Baltimore as a result of their claims. While piecing together the abuse that had gone on inside the school for decades, the victims began attaching it to Sister Cathy who some had confided in.

Investigations later showed that Maskell was not arrested or charged with the young nun's murder. In police probes about the sexual abuse, he denied all the accusations against him.

Armacost emphasized the fact he is not the only suspect in the ongoing case on Thursday, telling DailyMail.com there is at least one living suspect.

She would not disclose their identity or say how police were investigating any alleged links to the killing.

There are also other suspects who are now dead.

'We may never determine exactly who killed Sister Cathy but we hope to and we still feel we are able to.

The grisly murder haunted the city for years. Despite rampant suspicion among local residents that Maskell was involved, he never faced arrest

In 1994, police dug up boxes of records Maskell had ordered to be buried at Holy Cross Cemetery. They contained psychological health evaluations of girls he was accused of raping and also allegedly contained nude photographs of them but he was never charged. It is not known whether he was buried in the same cemetery

'If people die and their memories fade, witnesses fade, it becomes harder [but] we still feel optimistic that it may be possible to reach a resolution.

'If we had a situation that the DNA put someone at that scene, that would be a huge breakthrough,' she said.

The investigation into Sister Cathy's death prompted detectives to dig up documents in another Baltimore cemetery.

Former students said Sister Cathy asked them: 'Are the priests hurting you?'

In 1994, police were led to a patch in the Holy Cross Cemetery where a gameskeeper said Maskell had ordered him to bury the documents years earlier.

The unearthed papers were health evaluations of some of the girls he had been accused of raping and molesting .

One police officer who was interviewed by The Huffington Post in 2015 said the boxes contained nude photographs of the girls but that the images vanished once in the hands of the city's police department.

It would have been enough to jail Maskell for child pornography, he said, but they were destroyed and never seen again.

'We found hard evidence — these girls had their tops open. I saw them with my own damn eyes,' he said.

One of the former students interviewed in the Netflix documentary said Maskell once even took her to Sister Cathy's body before it was found by police as a threat to stay quiet about his abhorrent abuse of the girls in the school.

Jean Wehner said he drove her to the site and whispered: 'You see what happens when you say bad things about people?' as they stood over Sister Cathy's body.

She was too frightened to ever share what he had told her with anyone.

In a trailer for The Keepers, she said: 'I believe Sister Cathy was murdered because she was going to talk about what went on at Keough.'