Profiling has a bad name but a worse name than it deserves. Think through the following example if you need convincing.
A truck is driven into a crowded Christmas market in Berlin. A dozen people die and many more are injured, some very seriously. The original driver of the truck is found shot dead on the passenger seat. The person who drove the truck into the crowd flees the scene.
For a number of reasons, including the similarities to an incident in Nice on Bastille Day this year, it is a reasonable first assumption that this is some kind of terrorist attack. The fact that the driver runs off is worrying. First, because the person is probably armed - there is a body with gunshot wounds in the truck - and could use the gun again. Second, because if it is a terrorist attack under the flag of some Islamic cause, then the driver should really have died in the attack - that's the rule - unless he or she is going to make a further attack and probably in the near future in which they may seek to die. If this is a non-Islamic attack, the same reasoning applies: the driver may intend to kill again.
The police therefore are under enormous pressure. They have lots of resources but the clock is against them. Ideally, some kind of trail will lead them directly to the perpetrator of the attacks but it may not. They quickly decided that their first arrest was of the wrong person. Now they have a Tunisian identity card which may or may not be a false lead supplied to throw them off the scent. Maybe CCTV will show up something.Maybe forensics will find some fingerprints or DNA ...
The police would simply be failing in their duty of public protection if they waited for a definite lead. They have no choice but to profile.
Profile One: The driver will be male . I would bet heavily on that. Wouldn't you? The driver may have a female accomplice - a wife, for example - but the driver will be male. That Profile immediately lifts suspicion from 50% of the population. Why try to dodge that fact?
Profile Two: The driver will be over the age of 16 (probably over the age of 18) and that may have something to do with the logistics of getting hold of guns, hijacking trucks, driving them into crowds. At the other end, the driver will be under the age of forty. Terror attacks of any kind are very rarely mounted by men older than that. This Profile removes suspicion from another 25% of the population, roughly speaking.
So we are down to 25% of the population as potential suspects as a result of profiling. Now it begins to get difficult.
Profile Three: Will the driver be someone born in Germany or born elsewhere? This is tricky. Recent terrorist attacks in Belgium and France have involved both men locally born and men born abroad. So it would be unwise to profile by place of birth.
Profile Four: A Christmas market is an unlikely - in fact, implausible - target for a right-wing nationalist /neoNazi, white terrorist unless as a provocation. But as a provocation there is a risk it will backfire, and if it is a provocation, some effort would surely have been made to point the finger at refugees, immigrants, Muslims - whatever - as the perpetrators. The Tunisian identity card could be such an attempt to create a false trail. It's therefore not possible to rule out a right-wing attack. However ...
Profile Five: Most recent terrorist attacks in mainland Europe using improvised means and aiming at random deaths have been carried out by non-white individuals born in predominantly Muslim countries or brought up in broadly Muslim cultures. It would be irresponsible not to profile for a young, male, non-white, Muslim background. He could be German by birth but, if not, he could come from anywhere and could be a recent arrival in Germany or not. We are now down to maybe 10% of the population and that's still a hopelessly large number. That is one of the limitations of profiling as opposed to forensic policing.
How you get the 10% down to 1%, I don't know, but the most obvious next move is to profile who has been in Berlin for at least a week or so or who has accomplices who have been in Berlin for longer than that. Some preliminary research probably had to be done - where to find a truck to hijack, what route to follow to the market, what obstacles (if any) there were to getting into the market. It's possible that the driver has now left Berlin and it's possible he had a home base in another place to which he has returned. And so on.
Whatever the truth, I hope the Berlin police can profile down to 1% and even more I hope they get a lead from CCTV, fingerprints, DNA and so on.
Added later on 21 December: The Tunisian identity card is being treated by the police as a genuine lead because it links to someone already known to the immigration and security services. He is male, in the age group 18 - 40, is non-white and - if he is indeed Tunisian - comes from a predominantly Muslim cultural background.