In the beginning, they were known as die Dönermorde – the kebab murders. The victims had little in common, apart from immigrant backgrounds and the modest businesses they ran. The first to die was Enver Şimşek, a 38-year-old Turkish-German man who ran a flower-import company in the southern German town of Nuremberg. On 9 September 2000, he was shot inside his van by two gunmen, and died in hospital two days later.

The following June, in the same city, 49-year-old Abdurrahim Özüdoğru was killed by two bullets while helping out after hours in a tailor’s shop. Two weeks later, in Hamburg, 500km north, Süleyman Taşköprü, 31, was shot three times and died in his greengrocer’s shop. Two months later, in August 2001, greengrocer Habil Kılıç, 38, was shot twice in his shop in the Munich suburbs.

The crime scenes indicated that the killers favoured a particular killing method. Typically, several shots were fired at close range to the face. Most of the bullets were traced back to a single weapon, a silenced Česká CZ 83 pistol. Police assumed that the professional method of killing, as well as the intimate nature of the murders – when they died, the victims were presumably looking directly into the eyes of their killers – meant that the murders must have been carried out by Turkish gangsters fighting out turf battles. No hard evidence ever substantiated this theory. Nevertheless, the taskforce assigned by the German authorities to the case was given the name “Bosphorus”.

The Bosphorus team tried to persuade the widow of Enver Şimşek, the first victim, to say that her husband was connected to the Turkish mafia. They invented a false story of marital infidelity – that Şimşek was having an affair and had a secret family elsewhere – in the hope that her fury would lead her to reveal his non-existent underworld ties. She said nothing, but the police continued to waste time and resources attempting to prove the killings were the work of Turkish gangs.

Three years later, in 2004, Mehmet Turgut, 25, was murdered in a kebab shop in the city of Rostock on the Baltic coast. The next attack came later that year in the form of a bomb detonated in the Keupstrasse area of Cologne – a part of town popular among Turkish immigrants. Twenty-two people were wounded. In June 2005, İsmail Yaşar, 50, was shot in his kebab shop in Nuremberg – the third murder in that city.

The following year, a 41-year-old Greek-German locksmith named Theodoros Boulgarides was killed in his newly opened shop in Munich. He was the first victim without a Turkish background. In 2006, a kiosk vendor named Mehmet Kubaşık, 39, was shot in the western city of Dortmund. Only two days after that, Halit Yozgat, 21, was killed while sitting behind his desk in the internet cafe he ran in the central German city of Kassel, 160km away.

The killings occurred in seven different cities across Germany, and were often separated by months or years. This made it difficult to connect them, though no one expected it to take until 2006 for the authorities to grasp how they were related.

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From the very start, the investigation was riddled with basic errors and faulty assumptions. First, at least two of the murders took place at locations close to police stations, which should have made them unattractive sites for mafia murders. Then there was the problem of the two “Eastern-European-looking men” on bicycles whom eyewitnesses described leaving several of the crime scenes. More baffling still was a fact that surfaced during the investigation of Halit Yozgat’s killing: a German intelligence agent had been inside the cafe when the murder took place – something he later neglected to report.

In 2006, Alexander Horn, a young police profiler who prepared a report on the case for the Bosphorus team, began to cast doubts on the idea that the murders were connected to the Turkish mafia. In several cases, the victims were killed on days when they had broken with their daily routine, and were in places that no one could have predicted. It seemed more plausible that the victims had been chosen randomly by the killers, rather than singled out for vengeance by professional hitmen.

By using the same weapon, the killers also appeared to be drawing attention to their crimes and underlining the connection between them. Horn identified this as a typical tactic of far-right groups. Some officers were assigned to pursue this lead, but the focus of the investigation remained on the police’s initial theory. The media continued to refer to the killings as die Dönermorde.

In November 2011, more than a decade after the first murder, DVDs containing a curious recording were dropped off at the offices of several German newspapers. They featured a doctored episode of the 1960s cartoon series, the Pink Panther, which appeared to be a message from the killers. For the first few minutes, the Pink Panther strolls around a city, where he sees a poster calling on citizens to “Stand with your country” and “Stand with your people”. Accompanied by the jaunty chords of Henry Mancini’s theme song, the character bombs a grocery store – then the video cuts to news footage of a shop that had been similarly attacked in Cologne in 2001.

Facebook Twitter Pinterest A still from the doctored Pink Panther film that the far-right NSU sent to various German organisations, revealing their crimes. Photograph: Getty Images

The Pink Panther lounges on his couch and watches television news clips about the so-called Dönermorde. The clips flickering on his cartoon television are of real news reports from the murder scenes, with gruesome photographs of the victims. The Pink Panther’s eyes glaze over with boredom at how long it takes the German public to realise who is behind them. With a huff of impatience, the narrator indicates a sign on the screen: the murders, the video suggests, are the work of a group calling itself the National Socialist Underground (NSU).

By the time the German press was puzzling over the Pink Panther video, the investigators’ focus had finally narrowed to a cluster of extreme rightwing groups operating in the country. The authorities had still not figured out how to find the killers, but their confusion was brought to an abrupt end on 4 November 2011, when two men used bicycles in a bank robbery in Eisenach, a town in the central German state of Thuringia. After the robbery, they loaded the bikes into a rented camper van.

After a tip-off, police found the vehicle nearby. The two men had a vast stockpile of guns and ammunition inside the vehicle, but they did not try to fight their way out. Instead, according to investigators, they chose to kill themselves and set fire to the van. (An official report later concluded that one of the men had set the van alight, killed the other and then himself.)

The bodies were identified as those of Uwe Mundlos and Uwe Böhnhardt, two longstanding but hitherto unremarkable members of Germany’s enduring far-right scene, who had escaped the police with their friend Beate Zschäpe 13 years earlier. Even before identifying the corpses, investigators had found in their van the gun of a murdered police officer, Michèle Kiesewetter, whose killing five years earlier had never been solved.

Four days after the death of Mundlos and Böhnhardt, Zschäpe called the police in the Thuringian city of Jena. “Beate Zschäpe here,” she said. “I’m the one you’re here for.” The local authorities did not immediately grasp the significance of the call, even though more than a decade earlier the police had searched for all three in connection with a series of smaller crimes. German intelligence services had also been keeping tabs on the rightwing radical scene that Zschäpe was a part of, but had lost track of her, along with Mundlos and Böhnhardt when they went underground.

Facebook Twitter Pinterest The burnt-out apartment that was once the home of Uwe Mundlos, Uwe Böhnhardt and Beate Zschäpe in Zwickau, Germany. Photograph: Marco Prosch/Getty Images

The three had been living together in the town of Zwickau in an apartment that Zschäpe burned down after she learned of the deaths of Mundlos and Böhnhardt. When police later searched the scorched apartment, they found newspaper clippings about the murders of the Turkish-German businessmen, copies of the Pink Panther DVD, and the Česká pistol. This was early evidence that linked Mundlos, Böhnhardt, and Zschäpe to the murders that had first been investigated by the Bosphorus group.

On 6 May 2013, after two years of sensationalist speculation about the NSU in the German press, Zschäpe appeared for the first time in a Munich courtroom, charged with nine murders, an attack on police that included a murder, and two attempted murders by bombing. Four other men also stand accused of providing support to the NSU.

For the media, it was Bonnie and Clyde and Clyde – offering the salacious possibility of a murderous menage a trois

Rather than investigating how far-right killers could have operated undetected for so long, most of the German media opted for lurid coverage of the NSU, insisting that it consisted of only three people. Der Spiegel took the lead with a cover story dedicated to “ice-cold precision” of what it called the “Brown Army Faction”, with photographs that portrayed Zschäpe, Mundlos and Böhnhardt as natural-born killers, ready for their Hollywood close-ups. For the media, it was Bonnie and Clyde and Clyde – offering the salacious possibility of a murderous menage a trois. The German tabloid Bild ran the headline “The Devil has dressed up,” after Zschäpe appeared at the opening of the trial in a trouser-suit, jewellery and freshly dyed hair.

Zschäpe, now 41, has been sitting in court every weekday morning in Munich for the past three years, but she has revealed almost nothing – despite the urgent pleas of the families of the victims. While she claims that she now understands that Mundlos and Böhnhardt had conducted bank robberies and killings, she claims not to have known anything about their plans or activities while she lived with them. “They had become my family,” she said. Her plea is not guilty.

But the significance of the trial is far larger than what Zschäpe did or did not know about the killing spree. Germany’s sense of itself is also on trial. The findings of the prosecution suggest that Germany, a nation that prides itself on having confronted the dark recesses of its past with unique diligence, has left a thriving underground culture of rightwing extremism untouched.

Alternative für Deutschland – the first far-right populist party in Germany to enjoy sustained electoral success since the second world war – is only the latest in a series of symptoms of a widespread animosity toward the postwar liberal consensus. Darker currents of discontent are openly displayed on the internet – and on newsstands and television, where rightwing arguments have increasingly found favour.

The German government has been content to write off the NSU as a stand-alone terror cell of sociopaths – an unfortunate, but exceptional recrudescence of a political syndrome that the country has long since inoculated itself against. However, the NSU murder investigation and Zschäpe’s trial suggest that the organisation may have been carefully supported and protected by elements of the state itself.

The first thing to understand about the National Socialist Underground is that it was never really underground. Beate Zschäpe first met Uwe Mundlos when they were teenagers, at an after-school youth club in Jena, a renowned university town, perched on the slate mountains of the former East German state of Thuringia. It was 1991 and many East Germans were still feeling the shock of the fall of the Berlin Wall and acutely aware of how much they lacked in comparison to their western neighbours.

The youth club is still there today, set in a strip of single-storey buildings on a quiet street with dramatic views of the surrounding valleys. When we visited the neighbourhood earlier this year, it seemed normal enough: well-maintained apartment blocks, playgrounds full of children, direct trams to the city centre. A new school was being built across the street from the youth club, with placards advertising places for the children of asylum seekers.

There were a few ominous signs, though, such as the German flags that were hanging from a few high-rise balconies. Anywhere else, they would be an innocuous show of patriotism, but in this part of Germany the flag can send a different signal. Thuringia has long been one of the heartlands of Germany’s radical right. In the 1990s, the youth club was a focal point in the emerging far-right scene. Former supervisors at the club remember turning a blind eye – for fear of losing the trust of the cool kids – when teenagers gave each other birthday party invitations with small swastikas on them. At her trial, Zschäpe described meeting and falling in love with Mundlos during her adolescence in the late 1980s. Then on her 19th birthday, she met and fell in love with Mundlos’s friend, Uwe Böhnhardt, who was even more committed to the rightwing extremist cause.

Before the fall of the Berlin Wall, to become a neo-Nazi in East Germany was a form of youthful rebellion

Before the fall of the Berlin Wall, to become a neo-Nazi in East Germany was a form of youthful rebellion against the state. What better way to antagonise communist elites than to parade around as their old enemy? After 1989 and the fall of the wall, neo-Nazism became a conduit for rage against the pieties – and the perceived humiliations and betrayals – of the newly unified Federal Republic of Germany. West Germany’s identity had long been bound up with its productivity and wealth in comparison to East Germany. Meanwhile, its politicians and intellectuals embraced what the country’s leading philosopher, Jürgen Habermas, called “Constitutional patriotism”. It would be an identity based on a shared commitment to ideas rather than one founded on blood.

This new West German identity was something Zschäpe, Mundlos and Böhnhardt fiercely rejected. But there was nothing in their backgrounds that made them particularly susceptible to rightwing extremism. Zschäpe’s childhood does not appear to have been especially tumultuous, though she had a troubled relationship with her mother. (Zschäpe never met her biological father, who was Romanian.) The backgrounds of the two men are even further from the stereotype of the backward, resentful easterner. Böhnhardt’s father worked as an engineer and his mother as a teacher; Mundlos’s father was an IT professor at the Jena University of Applied Sciences. The parents treated their children’s developing interest in Nazi history and knick-knacks as a passing phase. (Although Zschäpe’s mother later reported that she was concerned when she heard that Mundlos’s grandfather collected Nazi curios.)

Uwe Böhnhardt. Photograph: Uncredited/AP

“Their experience was far from unique,” said Martin Debes, a journalist for the Thüringer Allgemeine newspaper, who grew up in Jena at the same time as Zschäpe and the two Uwes. “But in the youth scene at the time you often had to choose: become a neo-Nazi or a punk.”

Zschäpe started out as a punk, joining a nominally leftwing group known as “the Ticks” that got into fights with local neo-Nazis. But at the Jena youth club Mundlos and Böhnhardt encouraged her to switch sides, and in a few years the three of them had joined the flourishing neo-Nazi scene in the newly reunified Germany. They devoted weekends to battling leftwing punks in the streets and attending concerts of far-right bands such as Türkenjäger (“Turk hunter”) and Endsieg (“Final Victory”). Some of their early stunts included touring the former grounds of Buchenwald while dressed up in self-tailored SS uniforms, and inventing a board game called “Pogromly”, which rewarded players for sending as many Jews as possible to concentration camps.

The fall of the Berlin Wall offered East German neo-Nazis a new focus for their rage. As Turkish-Germans and Germans of other backgrounds began moving into the east, there were flare-ups and violence. Kebab stalls that sprung up in the tiniest towns of Thuringia became regular targets for young neo-Nazis. In September 1991, rightwing extremists attacked housing facilities for asylum seekers in Hoyerswerda, a town 200km east of Jena in the state of Saxony. The attacks were the start of a new brand of violence throughout Germany. During a three-day riot in the city of Rostock on the Baltic coast in August 1992, several thousand people surrounded a high-rise asylum shelter and watched while neo-Nazis threw Molotov cocktails through the windows. The building’s Vietnamese and Roma inhabitants barely survived by fleeing to the roof, and passing their babies up the stairs along a human chain.

The attacks were not confined to the former East Germany. On the night of 22 November 1992, neo-Nazis set fire to two houses of Turkish families in Mölln, a small town in the north-western state of Schleswig-Holstein. Two girls and a 51-year-old woman died in the flames. Nine others were seriously injured. In 1993, skinheads in Solingen, a town outside Cologne, set fire to the home of a Turkish family, killing five people, including three children.

This violence seemed senseless and random, but it was effective. All the major political parties of the time bowed to pressure applied by rightwing extremists. Helmut Kohl’s conservative coalition government called for new limits on immigration. In 1992 and 1993, his expanded coalition, with support from the Social Democratic party, changed the German constitution to limit the country’s obligation to admit asylum seekers. The far-right rejoiced at finding its arguments winning the day on mainstream TV.

For Zschäpe, Mundlos and Böhnhardt this was apparently not enough. After their early years of small-time crime, investigators claim that they began trying to build homemade bombs. In January 1998 the police, tipped off by an anonymous source, searched Böhnhardt’s garage in Jena and discovered 1.4kg of TNT – enough to destroy a car. By the time an arrest warrant was issued later that day, Böhnhardt had fled Jena. Together with Zschäpe and Mundlos, he later hid in the city of Zwickau, 80km to the east.

They allegedly conducted the longest, and most intricate, political killing spree in postwar German history

During their decade on the run, Zschäpe, Böhnhardt and Mundlos seem to have worked odd jobs and in shops that sold Nazi paraphernalia under the counter. At the trial, Zschäpe has been accused of helping the two men supplement their income with a series of bank robberies, which the three friends carried out together in a number of towns in Thuringia and Mecklenburg-West-Pomerania between 1999 and 2011. Sometimes they entered wearing gorilla masks, sometimes masks from the movie Scream. Their trusted escape method was allegedly to ride bicycles to a nearby rented van, in which they waited until the search for them had ended. The German police managed to link the robberies to each other, but not to Zschäpe, Böhnhardt and Mundlos.

The three fugitives showed few signs of concern about their possible capture. They used fake IDs and rented their apartment under aliases, but took few precautions beyond that. Neighbours fed their cats when they were away, and it appears that friends visited each week when they were home, sometimes bringing their children. With patience and an almost languid sense of impunity, Zschäpe and the two Uwes allegedly conducted the longest, and most intricate, political killing spree in postwar German history.

When we visited the Munich courtroom earlier this year, all eyes were trained on Zschäpe, who stared at her laptop and seemed more worried about running out of the crate of coconut water she had brought to the trial than anything that might happen there. With her neat long hair and signature trouser-suit, she appeared deeply at ease, smiling like a professional model for a brief press photo session, before she settled back among the lawyers, from whom she is almost indistinguishable.

In the press and visitors’ spectator booth, set behind glass above the courtroom, conspiracy-theorists, bloggers, newspaper reporters, and law students studying the trial all sit together – alongside a loyal Zschäpe groupie. (The most notorious of Zschäpe’s fans, Anders Breivik, the extreme-rightwing Norwegian terrorist, sent her a letter of solidarity from prison in 2012.)

Zschäpe originally seems to have chosen her defence lawyers on the basis of their martial-sounding surnames: Sturm (“Storm”), Stahl (“Steel”), and Heer (“Army”), but she soon turned against them. Four years into the trial, she has finally found a young lawyer she likes. The two whisper and smile during the court proceedings. The main judge at the trial, Manfred Götzl, has ordered the state lawyers she fired to remain in the courtroom because their departure could be grounds for an appeal: he wants to fend off any claim by Zschäpe that her current lawyer does not have full knowledge of the trial. Sturm, Stahl, and Heer sit a few chairs down from Zschäpe in what appears a state of permanent listlessness. Behind Zschäpe sits Ralf Wohlleben, a neo-Nazi accused of providing Böhnhardt and Mundlos with the Česká pistol used in the murders. His lawyer, Nicole Schneiders, first appeared in police reports on the extreme right when she was just 16 years old. The members of the extreme-right have taken up different, coordinated positions in the Munich courtroom. The lawyers and the accused sit side by side, and greet each other with kisses on the cheek.

The prosecution has decided to treat Zschäpe’s case strictly as a murder trial. She is essentially charged with being the last surviving member of the group of three who are assumed to be responsible for the killings. The task of the trial, in this view, is simply to clarify whether – and to what degree – she was involved with the killings. There has been little effort on the part of the investigators and prosecutors to determine whether other rightwing extremists were involved.

When one considers the level of local knowledge required to carry out these murders in several different German states – the detailed knowledge of getaway routes at the various crime scenes, the massive stockpile of weapons, the professionally forged fake IDs, not to mention the cost of these operations – the question of how the NSU could have operated without the support of a much larger network of sympathisers is unavoidable. Yet the prosecution appears at pains not to address this question.

Still, despite its slow-moving procedures and its limited scope, the proceedings have provided a succession of strange revelations about the workings of the German state intelligence agency, known as the BfV, and its state-level branches, known as the LfV, which have led to allegations that elements within the agency either turned a blind eye to the NSU murders or supported the group’s aims.

In summer 2013, Andreas Temme, the Hessian LfV agent who was inside Halit Yozgat’s internet cafe in Kassel when Yozgat was murdered, testified that he did not hear the silenced shots, nor did he notice the sprinkles of blood on the counter where he placed his payment in coins when he left. Spectators of the Munich trial agree that one of the most searing moments of the trial came when Yozgat’s father described how he found his dying son. It was impossible, he said, that Temme could have left the cafe without seeing the dead body behind the counter. “Why did you kill my son? What did he do to you?” he shouted at Zschäpe and Wohlleben in the courtroom.

Facebook Twitter Pinterest The Česká pistol allegedly used by the Neo-Nazi gang to commit multiple murders. Photograph: Alex Grimm/Getty Images

Temme, who denies any involvement, said that it was simply a coincidence he was in the cafe at the time of the murder and that he had been surfing dating websites. (“I was in the wrong place at the wrong time,” he said in an interview on German public television in July 2012.) When the police rounded up all those who were present at the scene of the murder, Temme did not come forward. After he was tracked down, Temme claimed that he did not volunteer any information because he was worried that his wife would discover his online proclivities. Yozgat’s father won approving nods from many in the audience at the trial when he declared: “We all know this man is lying.”

One of the prosecution’s witnesses, a policeman from the village where Temme grew up, testified that in his youth, Temme was known as “Little Adolf”. When the local police tried to dig deeper into allegations that Temme had a personal library of Nazi literature and weapons manuals, the interior minister of the state of Hesse, Volker Bouffier, shielded him from further investigations and from the press. Bouffier, who is now the prime minister of Hesse, argued at the time that it was necessary to protect Temme in order to “guarantee the protection of undercover agents”. The brazenness of Temme’s testimony ignited anger in the German press about the prerogatives of its intelligence agencies, but it has since mostly subsided. Temme has meanwhile retired from the LfV, but continues to draw his pension.

Germany’s domestic intelligence service is charged with protecting the national constitution – from both foreign threats and domestic extremism on the left and right. But its record with regard to the latter has not always been stellar. In recent decades, it has tended to use paid informants who are already deeply entrenched in extremist milieus.

In the case of the country’s far-right scene – whose membership the BfV estimates to number 23,850 as of last year – these informants are not simply turncoats who make some money on the side by giving tips to police. Instead, they are lavishly groomed sources who are developed over long periods, promised legal protection, and plied with funds that elevate their status in the movement.

By distributing cash to their informants, the BfV has hoped to create a paper trail that maps out connections between the far right across Germany. But in practice, this dispersal of money has also nurtured rightwing groups, providing them with a level of funding they would not have been able to obtain from their genuine followers. “There’s no question [that the] BfV overdid the financing of informants during the early 1990s,” said Hajo Funke, a professor of politics at the Free University of Berlin, who is the author of a book on the NSU.

Before he was imprisoned in 2014, Tino Brandt, the man who first welcomed Zschäpe, Böhnhardt and Mundlos into the rightwing extremist scene in Jena, openly boasted to German public television that the state had given him 200,000 Deutsche Marks (roughly €100,000) in the early 1990s to print flyers and organise concerts and demonstrations. For his fellow neo-Nazis in Thuringia, Brandt’s work as a paid informant was an open secret. He never gave the state useful information, but his funds made organisational growth and the recruitment of young neo-Nazis possible. (Brandt himself was never tried for his connections to the NSU and far-right violence, but was sentenced to five-and-a-half-years in prison on 66 counts of child sexual abuse and child prostitution.)

In March, Judge Götzl took an hour to explain to the courtroom that the task of the NSU trial is simply to judge the accused, not to investigate what German intelligence agents knew or did. The following month, Götzl rejected a petition from lawyers representing the victims’ families to introduce a witness who was a BfV informant in Zwickau at the time of the first killings, when he almost certainly knew the members of the NSU.

Ralf Marschner, an avowed neo-Nazi and a former singer in a skinhead band called West-Saxon Riff-Raff, was a paid informant for the BfV between 2000 and 2002. During these years, he lived around the corner from Zschäpe, Mundlos and Böhnhardt. “Marschner was the main Neo-Nazi in Zwickau, which is a relatively small town,” says Dirk Laabs, an expert on the NSU.

But when a government commission that was reviewing the NSU investigation tried to obtain Marschner’s file, it was told by a public prosecutor in Saxony that “a flood has destroyed the file”. According to Funke, Marschner is one of the most important witnesses, because he “proves that the BfV almost certainly would have known about the two Uwes and Beate, either directly through Marschner, or by monitoring his activities”. (Marschner, who is currently living in Switzerland, has refused to comment on the case to the press.)

Earlier this year, the Munich courtroom learned that when Marschner was working as a paid informant for the BfV, he probably employed Mundlos in his construction company. It also seems likely that Zschäpe worked in his clothing shop, Heaven and Hell, which sold Nazi T-shirts and paraphernalia under the counter. The exact nature of Zschäpe’s work for Marschner remains remarkably unclear. These connections make Marschner a critical witness for the prosecution. And yet Judge Götzl has dismissed the effort to explore his role, describing his alleged employment of two NSU members as “irrelevant”.

According to Bilgin Ayata, a professor of political sociology at the University of Basel, who has researched the case and the trial, these omissions are typical of the state’s unwillingness to examine the more disturbing implications of the NSU murders. “Instead of acknowledging the institutional racism that the case reveals,” Ayata said, “the state has presented its investigations as a series of unfortunate mishaps”.

Zschäpe’s trial is the most significant courtroom showdown in Germany since the trial of the Baader-Meinhof gang – a radical-left terrorist group also known as the Red Army Faction, who targeted US military installations, conservative media outlets and German corporations in the 1970s. Both cases go to the heart of Germany’s identity in postwar Europe. In the Baader-Meinhof case, the question was whether German youth were willing to be integrated into western capitalism, and whether the German state would lapse back into a form of authoritarianism. In the Zschäpe trial, it is a question of how far Germany really is from becoming a nation of immigrants and how far the values of tolerance have penetrated society.

“The Red Army Faction wanted to bring down the German state,” said Hajo Funke. “The difference this time is that the National Socialist Underground got some help from part of the state.”

The head of the BfV, Heinz Fromm, resigned in 2012 while facing public pressure over the mishandling of the NSU investigation, but he never mentioned the reason for stepping down, nor has the BfV admitted any improprieties.

Instead, BfV officials have strenuously guarded their sources and intelligence from both the normal police and from a special federal commission that was established in 2012 to probe lapses in the NSU investigation. But critics of the federal commission allege that it has also failed to dig deeper into the inconsistencies in the case. “The Federal Examination Commission has chosen not to question the claim that the NSU was confined to three people,” said Bilgin Ayata.

Facebook Twitter Pinterest A rally in Berlin, in 2012, to commemorate the murder victims of the neo-Nazi group. Photograph: Carsten Koall/Getty Images

The BfV has long been regarded as right-leaning: it was founded after the second world war by the Americans, who welcomed Nazis and former Gestapo members into its ranks. Its mission was to spy on and root out the KPD, as the German communist party was known, as well as members of the Social Democratic party. The first head of the organisation, Otto John, defected to East Germany in 1954, citing the overwhelming number of Nazis in the organisation. His successor was Hubert Schrübbers, a former member of the SS. Under Schrübbers’ supervision, the German communist party was finally banned in 1956, based on allegedly incriminating materials turned up by the BfV. Major German political parties – such as the Left party and the Greens – have long called for the abolition of the BfV.

For now, neither police nor trial investigators have the right to subpoena BfV documents that may contain vital evidence about the NSU killings.

There are still many mysteries about the true extent of the seven-year killing spree – most notably the circumstances of the final murder, of the police officer Michèle Kiesewetter, which did not fit the pattern of the others. The prosecution has accused Mundlos and Böhnhardt of attacking two police officers on duty in the town of Heilbronn in April 2007: Kiesewetter, age 22, was killed instantly; her duty-partner survived but has no memory of the attack.

A nightly news report about the murder scene appears at the end of the Pink Panther video, and traces of Kiesewetter’s DNA were found among the charred remains of the Zwickau apartment that Zschäpe set on fire. But a different type of gun was used for Kiesewetter’s murder, and witnesses at the scene describe more than two people running away from the scene with blood on their clothes. Local police have declared these witnesses unreliable, and stated that only Mundlos and Böhnhardt were involved in the murder. But their reason for killing a police officer remains unknown, and the possible presence of others at the crime scene has further stoked fears that the NSU was not an organisation of only three people.

“For the commissions and for the trial, the [size of the] NSU is a fait accompli,” Ayata said. “They ignore the questions that nag at the migrant communities in Germany: Are they still here? Are they still killing?”

At a public commemoration of the victims of the NSU murders at the Konzerthaus Berlin in 2012, Angela Merkel asked for forgiveness on behalf of the investigators who had insisted that the victims were entangled in the Turkish mafia. “As chancellor, I will do everything I can to clear up the murders and uncover the accomplices and supporters, and bring all of the perpetrators to justice,” she said. But her government is hesitant to probe more deeply into the more troubling elements of the case, and of the rightwing extremist scene that continues to flourish in Germany.

More than three years into the trial the judges seem bored; they appear to have lost interest in key witnesses

There is a telling contrast between the laxness of Zschäpe’s trial and the professionalism of the concurrent prosecution of the so-called “last” Nazi, Reinhold Hanning, a 94-year-old former Auschwitz guard. Hanning’s trial was swiftly wrapped up in four months, and he was sentenced to five years in prison for “facilitating slaughter” at the extermination camp. It seems that Germany may be more comfortable trying former Nazis than current ones. More than three years into Zschäpe’s trial, the panel of judges now seems bored; they take frequent recesses and appear to have lost interest in key witnesses.

Where German officials have feared to tread, dramatists have rushed in. The NSU murders have already been the subject of several films and plays, including a miniseries that aired on German public television, and a play by the Austrian Nobel laureate Elfriede Jelinek.

But theatrical versions of the trial cannot capture the complexity of the case, which seems impossible for anyone to fully grasp – especially when so much information still remains secret. Even the numerous fact-finding commissions established to review the botched investigation have had trouble assembling an accurate version of events. Most of the commissions have no authority to visit and search the BfV files. Instead they request files of interest, which the BfV delivers abridged and redacted. “We haven’t been granted the power to seize their files,” said Petra Pau, a parliamentarian for the Left party and a member of the federal commission looking into the case. “Not to mention the files they may have already shredded.”

One core problem is that too many expectations have been heaped on a trial that cannot bear them all. The victims’ families want justice and redemption, the judge wants no loose ends that could be grounds for a retrial, migrant communities want to know if they are safe from future attacks and terrorism, and political activists want to know whether the BfV was involved in a cover-up.

New pressure from Merkel’s government would be necessary to force BfV operatives to cooperate as witnesses. But there have been no steps in this direction. Meanwhile, the refugee crisis has fuelled Alternative für Deutschland’s rise to double digits in the polls, while hostility towards foreigners has become openly acceptable.

The German ministry of the interior counted around 14,000 far-right-related crimes in 2015, about 30% more than in the previous year. By April 2016, police counted three attacks per day against housing facilities for asylum seekers. Last year, a small group – one woman and two men – threw a molotov cocktail into a Zimbabwean child’s bedroom at an asylum centre in Lower Saxony. The savage anti-immigrant climate of the 1990s is making a return.

“The National Socialist Underground still has members out there,” said Petra Pau. “The question is only how many.”

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• This article was amended on 16 December 2016 to correct the distance from Jena to Zwickau. An earlier version of this piece also stated that Andreas Temme was a BfV agent. He was, in fact, an LfV agent. The article has also been amended to correct the spelling of Ralf Marschner’s name, to state that Zschäpe called the police four (rather than two) days after the deaths of Mundlos and Böhnhardt, and to make clear that Zschäpe first appeared in court on 6 May 2013, not on 11 April 2013 when the trial itself began.