The suspect is a "German WITHOUT a migration background": That's what the police in the southwestern German city of Mannheim posted on Twitter after a man drove into a crowd in the center of nearby Heidelberg in February, killing one person and wounding several others. The police were addressing rumors circulating on social media about the man's origin, as well as accusations that they were deliberately keeping mum on his ethnicity.

Such situations are part of a larger debate that the German media has been engaged in for a long time: Should journalists publish details about a criminal's ethnicity or not?

"Why is it necessary to know that the suspect is a Serb or a Turk or a long-time Frankfurt resident to understand a robbery at a kiosk?" asked Nikolaus Jackob, managing director of the Institute for Journalism in Mainz. Typically, the German media does not include details about a person's background in such cases. But more and more, nationality is playing a bigger role in reporting about crime.

The thefts and mass sexual assaults of women during the 2015/16 New Year's Eve festivities in Cologne were a turning point in the debate. Witnesses described the perpetrators as young men of "North African or Arab descent." And there was plenty of criticism about the way the assaults were reported, with people saying that the media were deliberately avoiding any mention of the men's ethnicity. Initially, most German media outlets did not report on this aspect, following professional ethical guidelines.

Read: Reporting on rampaging migrants and child-killing Germans

Press council adjusts guidelines

But public pressure did have an effect on the way German media are covering such stories. A recent study by the University of Munich showed that several weeks after New Year's Eve, newspapers tended to mention the ethnicity of perpetrators much more than they did previously. However, crime statistics show that there was no marked increase in the number of foreign criminals during that period.

The German Press Council has now adjusted the guidelines for reporting crimes, making them a bit looser than they were before. If it's in the "public interest," then the naming of an ethnic, religious or other minority is now justifiable. Previously, there needed to be a concrete connection - a story about the Italian mafia, for example.

The German media treads carefully with the issue of nationality and ethnicity - even when reporting crimes - because of the widespread discrimination and persecution during the Nazi era. Jackob says German press culture is very different from other countries such as the United States or Britain, where journalists tend to be much tougher when reporting on certain topics, particularly when the stories involve celebrities or criminals.

A matter of judgment

According to Jackob, German journalists have been forced to reflect on how they should respond to accusations that they are hiding something. They have to then decide whether to give in to the pressure, or maintain the principles they've followed in the past. Should journalists act in a way to appease the cries of "Lügenpresse" (lying press) that routinely come from supporters of the far-right scene and the anti-immigrant Alternative for Germany party?

Private broadcaster n-tv decides how to respond on a case-by-case basis. "Our aim is always to provide our viewers with comprehensive coverage, and not to patronize them," the station's editor-in-chief, Sonja Schwetje, said.

Public broadcaster ZDF says it only names the nationality of a suspect or criminal if is relevant to the incident - but that can be a complex question of judgment.

And then there's the "Sächsische Zeitung," based in the eastern German city of Dresden. Since July of last year, its policy is to always report the nationality of people who commit crimes. This was prompted by a reader survey carried out by communication scientist Lutz Hagen. He said that almost half of those surveyed thought that journalists had been ordered to leave out the ethnicity of criminals because of the current migration crisis. He also found that people tend to vastly overestimate the proportion of crimes committed by foreigners, compared to actual crime statistics.

Another survey is due to be conducted in a year's time. Hagen's hypothesis is that reporting about the nationality of criminals will result in readers' being better able to more accurately assess the share of crimes committed by foreigners.

But the experiment could also have negative consequences, says Georg Ruhrmann, an expert on the portrayal of migrants in the media. "Depending on the attitudes and routines of individual journalists, you could see more stereotypes or discriminatory statements filtering through," he said. And that could appeal to readers who themselves hold racist or anti-immigrant views.