Safia S., 16, is charged with "attempted murder, grievous bodily harm and support for a foreign terrorist organisation", a crime which carries up to ten years in jail.
"The federal prosecutor has asked for a youth penalty of six years' imprisonment for 16-year-old Safia S.," said the court in the northern city of Celle, where hearings are being held under closed doors as the accused is a minor.
Prosecutors said the German-Moroccan national, who is believed to have been radicalized as a young girl, had sought to catch the attention of police officers by following them at the main train station in the northern city of Hanover.
As the officers called her over for an identity check, Safia S. allegedly stabbed one of them in the neck with a vegetable knife before being overpowered by another officer.
Prosecutors say the teenage girl was "motivated by members of Isis in Syria to commit this act" on February 26th last year.
Meanwhile, they are seeking three years' imprisonment for 20-year-old Mohamad Hasan K., who is also on trial for failing to report Safia's plans to police.
The defence is expected to enter its plea on Friday, with a verdict scheduled for next Thursday (January 26th), the court added.
Germany was hit by a series of jihadist attacks last year, with the deadliest occurring on December 19th when a Tunisian suspect rammed a truck into a crowded Christmas market in Berlin, killing 12.
The suspect Anis Amri, who was shot dead days later by Italian police, had sworn allegiance to Isis.
Two attacks last July were also claimed by Isis - an axe rampage on a train in Würzburg that injured five, and a suicide bombing in Ansbach in which 15 people were hurt.