If he got off on a technicality would he, therefore, be innocent? Was OJ innocent or was he found "not guilty"?
Did OJ kill his wife? Almost certainly. But by law he is innocent, and if you or I were to walk up to him and kill him, the law would charge us with murder — and rightly so.
Remember that the purpose of a trial is not to determine the existential guilt of the accused. It is to determine if he has violated the law. Since only God knows everything, a trial before a judge or jury represents a best-we-can-do-as-humans approach to establishing justice under law here on this earth. The power to establish existential justice is reserved to God; therefore, to do more than try people under the law is to play God. This is why I oppose the death penalty except in cases where there is simply no other choice, i.e. when the convicted by his mere existence represents a clear and present danger to the community.
If a man is accused and found innocent at trial, then he is innocent — of breaking the law established by the State. Whether or not he is innocent of violating God's law is a matter best left to God.