Is it permissible to ask a friend to give false testimony to save someone from prison and deportation, knowing that the witness will state the truth he heard from other parties, but will attribute it to a different source so that it may be accepted in court?

The testimony should be based on what the witness heard. If your friend heard this statement from your adversary, then he may testify to what he heard; in fact, he must do so to ward off injustice and harm from you, for Allah Almighty says: "And do not conceal testimony, for whoever conceals it - his heart is sinful." However, if he did not hear this statement, then he is not permitted to lie in his testimony, because false testimony and lying are forbidden, even if the intention behind them is to reach the truth.