"This is the group where we are most likely to see such clashes, it is the highest risk group."
Activity after Sunday's Group B matches showed police were well prepared to deal with troublemakers and that cooperation between officers and hooligan experts from other competing nations had paid off.
"We saw in Klagenfurt the German police officers really know their fans very well and have acted at the right time," added Mathe.
"Often hooligans have bad family backgrounds where they experienced violence... "
Harald Mathe,
hooligan expert |
About 3,000 police were on duty in Klagenfurt at the weekend including 400 German officers.
Hooligan experts classify fans in three categories.
So-called 'A fans', who just want to enjoy the game, make up between 80-90 per cent of supporters.
'B fans', who account for around 10 per cent, can turn violent after excessive alcohol consumption or when their team are losing.
'C fans', the smallest group, use football as an opportunity for violence, said Mathe.
Bad backgrounds
"Often hooligans have bad family backgrounds where they experienced violence and where they learned conflicts are tackled or solved with violence," he added.
However age and gender also played a major role, Mathe said.
"Most of them are men chock full of testosterone and need to get rid of all their energy."
Law-abiding fans heading to the stadiums or fan zones have little to fear from troublemakers given the security available and the nature of hooliganism.
"Real hooligans are only interested in other hooligans," said Mathe.
"The normal fan has not much to be afraid of, though in general one thing is best, keep as far away as possible from hooligans or groups which are under the heavy influence of alcohol."