Anis Amri was one of the 549 "threats" known to authorities. Just using the word "threat" shows how difficult it is for police and intelligence agencies to deal with potential terrorists, for someone under surveillance who merely poses a danger cannot be seen as a suspect. First, a crime must be committed. In the case of Amri, however, the authorities did actually have information regarding his propensity for violence long before the Christmas market attack.

Could the attack that left 12 people dead and 50 injured have been prevented? This question cannot be clearly answered, but the details that are slowly becoming known cast the authorities in a bad light. According to media reports, Amri had searched the Internet for bomb-making instructions and weapons. There was evidence of his willingness to carry out an attack, and apparently he had contacts with Salafists and the so-called terrorist network "Islamic State" (IS).

Many agencies, too much information, how many mistakes?

There have been no official confirmations of the often astonishingly detailed descriptions, but no one has denied them, either. That is why there is reason to believe that they may be true. The tragedy would then be that the Gemeinsames Terrorismusabwehrzentrum (GTAZ - Joint Counter-Terrorism Center) in Berlin did not properly piece together the clues in the end. Forty different federal and state authorities work together with GTAZ, an organization that acts as an interface. Its terror experts analyze the threat potential on a daily basis. Even the alleged Christmas market attacker Amri was often a subject of discussion. The high degree of danger he posed had obviously been underestimated.

Whether this assessment can be labeled negligent may have to be investigated in detail by a parliamentary inquiry committee. Politicians from the Green Party and the Left Party are openly speculating about this. However, these two parties normally emphasize the importance of separating police and the Office for the Protection of the Constitution, a domestic intelligence agency. Close ties with the GTAZ are looked at skeptically - or are even unwanted - by the two opposition parties in Germany's parliament. The same attitude can also be seen with regard to video surveillance, which has long been a component of Germany's security infrastructure.

Never-ending discussion

The benefits of video surveillance cameras in public spaces are also controversial. Advocates point out investigatory successes, like the probe into the attempted murder of a homeless person in Berlin. But this had nothing to do with terrorism. Skeptics of video surveillance fear that Islamist attackers may deliberately select targets with video surveillance to better publicize their exploits. Similar considerations may have played a role when Amri's cell phone was secured as evidence. The analysis of the phone card led to the arrest of a Tunisian suspect. The phone may have been planted on the scene to put the authorities on the wrong track. Nonetheless, investigators did not find enough information for an arrest warrant.

According to currently available information, Amri could have been put in prison for crimes or for his planned deportation. Even the Federal Office for Migration and Refugees (BAMF) had known for some time that the Tunisian attacker was living in Germany using different identities. The exchange of information with GTAZ allowed other government organizations to access the information. Yet, the threat was underestimated. Could it be that other "threats" were classified as even more dangerous?

Threat potential was known

Security officials and leading politicians like German Interior Minister Thomas de Maiziere are constantly pointing out that the amount of staff needed for full surveillance is lacking. For years, authorities have been talking about the threat potential in Germany, especially whenever other European countries like France are targeted in attacks. Officials were especially nervous after the series of attacks in Paris when an international soccer match between Germany and the Netherlands was canceled at the last minute.

That decision was also based on findings and analyses made by security forces. However, there is a big difference: it is actually quite easy to cancel a sporting event. On the other hand, arresting someone considered to be a threat is much more difficult. Closing the gap in the complex security structures has long been a priority in the tense political debate about terrorism. Some call for stricter laws, others for the application of existing ones. Whatever conclusions are drawn - no one can ever guarantee that an attack like the one in Berlin will never happen again.