The answer to your question is not as simple as you might think. The fact that they did not intend to charge the co-conspirator does not mean that he should not have been advised of his rights. Unless he was given a grant of immunity or a promise in writing that he would not be charged, he still had the right to remain silent and not incriminate himself. Were his rights given to him? Did he testify? What did he say? I am assuming that he said he and your friend had an agreement to do something and that your friend was found guilty of conspiracy. If so, this issue should be raised on appeal. His appellate lawyer should proceed with this and any and all other issues whcih were raised in your friend's case.
Although I do not know why they would not want to also prosecute the co-conspirator, that does not automatically mean that your friend cannot be charged with the same offense. You are correct that it takes at least 2 people to make a conspirator and that the prosecutor has an obligation not to bring charges he cannot prove. Your appellate attorney will have to carefully go through the record of trial and ifdentify all issues to be raised on appeal and make a strong argument why your friend should have been found not guiolty or at least deserves a new trial.
I hope this helps. If you or your friend have any further questions, please feel free to contact me directly at [email protected] or at 757-420-9321.
