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The question of interest will be dealt with by the courts as part of the present case. If the Supreme Court upholds the Appeal Court decision no doubt Amaral's lawyer will apply for interest on the frozen funds just as Duarte did. He is also entitled to an amount towards his other costs. It's possible there will be claims from the other defendants also.
If Amaral is found innocent then he was clearly damaged by this case. At the very least he lost the use of his funds for seven years.
The problem for Amaral in pursuing a case along the lines you suggest is that the burden of proof lies with him.
The Courts will definitely demand to see his financial records as will the McCann lawyers (bet they can't wait).
Investigation of his finances has caused problems for him in the past ... then perhaps he is a man who learns nothing from history ... all may be revealed in the fullness of time ... bird in the hand and all that.