Now how did Amnesty International collect its information? What are the sources? Here are the answers.

So basically, the four sources from which Amnesty International collected its data on prison victims in Syria are ALL opposition sources. But read the technical report about how AI "cleaned" the data to reconcile different versions and change dates of birth and such.  Of course, Syrian regime is capable of the worst crimes (as are the rebels) but all media coverage and Western human rights reports about Syria are not reliable and reflect the political interests of one side.