Martyrs suffer as innocents. Criminals are punished for crimes. Criminals are not martyrs, and martyrs are not criminals. Criminals receive due punishment, martyrs endure undeserved punishment.
You see, there is merit if, in awareness of God, you put up with the pains of undeserved punishment; but what glory is there in putting up with a beating after you have done something wrong? The merit in the sight of God is in putting up with it patiently when you are punished for doing your duty. This, in fact, is what you were called to do, because Christ suffered for you and left an example for you to follow in his steps. He had done nothing wrong, and had spoken no deceit. He was insulted and did not retaliate with insults; when he was suffering he made no threats but put his trust in the upright judge. (1 Pet. 2:19-23)
Accordingly it is appropriate to say that Bonhoeffer suffered as a criminal, but it is inappropriate to say that Bonhoeffer suffered as a martyr.