Terror mastermind gets away?

It seems that the lady justice was left baffled when most of the suspects in the Madrid train blast were found guilty but the mastermind behind the whole affair,Rabei Osman was acquitted of the whole thing.
It is surprising that circumstantial evidence could be considered against the other accused but when it came to the ringleader.Rabei Osman, the Spanish judge Gomez Bermudez, decided to acquit him of the charges. Personally I do not think that the Judge should have let the ringleader get away especially since the police have a taped conversation between the accused and another person, in which he had confessed to being behind the whole affair. What is puzzling me is that since Circumstantial evidence was relied upon to find the other accused guilty then why was not the same Circumstantial evidence used to find the main ringleader guilty as well?
Frankly I think that this whole aspect of Circumstantial evidence should have been used against Rabei Osman as well. But his lawyers had argued in the courtroom that the translation of the taped conversation was all wrong and that Rabei Osman was not the ringleader behind the Madrid bomb blasts. Either way, the Judge accepted the ringleader's legal Repertoire and now he gets to walk away from the Madrid case!

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