The court decided to exclude the media from the trial that started on Thursday, aiming to protect the young defendant from "continued exposure and the related stigma."

Another 20-year-old suspect is also facing charges for not reporting Safia ahead of the February stabbing.

The knife attack in Hanover was the culmination of a long process of Islamic radicalization. Safia S. told police that her attack had been spontaneous. But investigators are telling a different story: The search for a motive quickly led authorities to believe that it may have been a terrorist attack. Safia S. is suspected of having contacts to radical Islamists. Surveillance video from the Hanover train station show Safia S. staring at two police officers as they move through the station. Because the officers find that she is acting suspiciously, they ask to see her ID. Then she attacks.

A search of the contents of her cellphone expose her long path to radicalization. In their search, investigators found chat transcripts between Safia S. and members of IS. According to an investigation conducted by North German Public Radio's (NDR) "Panorama 3," program  Safia apparently wrote the following in a chat from November 14, 2015 - the day after the Paris terror attacks: "Yesterday was the happiest day of my life, Allah bless our lions, who were in action in Paris yesterday."

The German-Moroccan girl wears a headscarf. Online, the high school student presents herself like so many others her age: selfies in front of her bedroom mirror, photos with girlfriends, images of cats. She swoons for Justin Bieber and Allah. "A girl that quotes the Koran is not a threat," her father says in an interview with NDR. Her mother gave her a devout upbringing. She had to go to mosque every Friday and she memorized the Koran. Yet that is where the young girl came into contact with men who were dangerously manipulative.

Did authorities underestimate the threat?

In 2008, at the age of seven, Safia S. appeared alongside the controversial Salafist preacher Pierre Vogel in a YouTube video. In it, she recites Koran verses with a soft voice. Vogel presented her as "our little sister in Islam" in Salafist propaganda videos, and when presenting her to supporters, as follows: "This is the new generation of Muslims, I am proud of you. Learn the Koran by heart and on Judgement Day you will move up a step for each verse you recite."

The investigation has shown that authorities in Lower Saxony had videos like these before the knife attack. The state domestic intelligence office was even investigating the young girl for preparing a serious crime in November 2014. Safia S. is also said to have had contact with the 20-year-old German-Syrian Mohamed Hasan K. Federal prosecutors are currently investigating him as a suspect involved in planning the supposed terror attack that led to the cancellation of an international soccer match in Hanover. Since he had knowledge of Safia's plans he is also a co-defendant in her trial. K. was able to flee Germany, but was arrested in Greece at the end of September.

What brought on the knife attack?

Safia's family was not blind to her radicalization. Even her grandmother called the police to inform them. Authorities got in touch with the family in mid-December and met with them in mid-January. Safia's radical ideas finally became evident when she left the country on January 22. She flew to Istanbul - her destination: IS in Syria. Her brother had already left just a few weeks earlier. But Turkish authorities detained him at the Syrian border. 18 years old at the time, he was then sent to prison.

After she left, Safia's mother reported her daughter missing to local authorities. Then she went after her daughter. In February, mother and daughter returned to Germany. The police were waiting for them when they arrived at Hanover airport.

First 'IS' attack in Germany

According to federal prosecutors, the teenager contacted IS members in Istanbul, at which point she was contracted to carry out a "martyr attack" in Germany. She also uploaded a video to an internet news agency claiming responsibility for a terror attack. It was not until March that authorities found IS instructions for a knife attack. Therefore authorities now consider the train station attack to be the first IS contracted terror attack in Germany. She faces up to ten years in prison.

Fatal mistake

Ever more mistakes have been uncovered in the ongoing investigation. Meanwhile, an investigative committee of the state parliament in Hanover is looking into the case. Could authorities have headed off the threat by detaining Safia S. in early February? A teacher and a school administrator contacted authorities after her detention at the airport as well.

A precarious memo sent to federal agencies by the State Office of Criminal Investigation of Lower Saxony (LKA) is among the investigative mistakes that has been discovered. The memo contains the line, "All-clear in the case of Safia S." And further: Upon examination, no concrete connection to IS found. The 15-year-old poses no threat. The date: February 25. Just one day later that assessment turned out to be a grave miscalculation.