There are two so-called "political prisoners" that all the Trotskyist grouplets I follow champion: Mumia Abu-Jamal, and Lynne Stewart. My primary sources of information about both these cases come from Socialist Viewpoint, Socialist Action, and The Militant, in approximately that order of importance.
Mumia, a long-time Black activist involved earlier with the Black Panther Party, was convicted of the 1981 murder of policeman Daniel Faulkner. He spent 30 years on death row until the sentence was eventually commuted to life in prison. His case is now finally settled--he has few if any avenues of appeal left open. The original trial apparently was something of a circus. Mumia started by defending himself, but being obviously incompetent as a lawyer he was assigned an attorney. Subsequently he claimed (perhaps with justification) that the judge was racist and that the jury was all white. Multiple levels of appeal have not found cause to overturn the conviction--the only real matter of dispute was whether the death penalty should stand.
Lynne Stewart was a progressive civil rights lawyer--somebody who in the old days would have at very least been known as a "fellow traveler." She defended the blind sheikh, Omar Abdel-Rahman in his trial on charges related to the first World Trade Center bombing in 1993. Mr. Abdel-Rahman was convicted, and because of his terrorist connections was placed under "Special Administrative Measures," designed to restrict his communication with conspirators outside. Ms. Stewart was arrested on assisting Mr. Abdel-Rahman in violating those measures, and eventually convicted and sentenced to ten years in prison.
Both of these figures proclaim their innocence. Mumia just flat-out says that he's innocent, without in anyway seeking to rebut the evidence against him. Ms. Stewart maintains that she simply acted as a good defense attorney, and that in any case the Special Administrative Measures are an unconstitutional infringement on her rights of free speech and freedom of association.
Now there are innocent people in jail. Indeed, there is a worthy organization known as the Innocence Project that is dedicated to freeing as many of them as possible. (Neither Mumia nor Ms. Stewart are on their list of clients.) Most innocent prisoners are victims of busy prosecutors, lazy cops, vengeful witnesses, tired jurors, and overworked, incompetent public defenders. Sammy Jones and Johnny Smith are not convicted after due process, but more likely they just fell through the cracks of a creaking and overworked criminal justice system.
How different this is from the cases of Mumia & Stewart. While Mumia turned his own trial into a farce, the case has been thoroughly reviewed in the subsequent thirty years of appeals. Likewise, Ms. Stewart (who clearly had competent counsel) has had multiple reviews of her case, and has lost every appeal. Unlike the clients of the Innocence Project, this pair has due process coming out the wazoo. I suppose there is some mathematical chance that they're innocent, but I think the odds of that are vanishingly small.
So what is it that makes these political prisoners? Both of these people claim that they, uniquely, are targets of government repression--somebody is out to get them. Mumia talks about the "Mumia exception to the constitution." Unlike the pedestrian injustice cataloged by the Innocence Project, this (according to their defenders) is a purposeful, conscious rigging of the system to "railroad" brave people to jail. In a word, it's a conspiracy theory.
For thirty years, Mumia has loudly and consistently proclaimed his innocence. I think he actually believes he's innocent, but then I think he's a psychopath. Now I've never met the man, nor am I a clinical psychologist, but he certainly shares some characteristics common with psychopaths. First, psychopaths always think they're innocent--by definition they have no conscience and thus are incapable of feeling guilt the way normal people do. Mumia's claim of innocence is not that he didn't commit the murder, but rather that there was nothing wrong about murdering the guy, and he shouldn't be in jail for it.
Second, psychopaths tend to be superficially charming and charismatic. Mumia definitely fits this category--supporters and do-gooders who visit him come away charmed (see here, for example). And there is no doubt that he is a talented man. Early in his criminal career he was introduced as a poet, as if poets couldn't be guilty of murder. He clearly knows how to write, and has acquired a considerable education. But I hazard that people who know him better--guards and other prisoners--have learned not to trust him at all.
Finally, Mumia has never shown any remorse. He has never reached out to the family of the victim, nor ever asked what he could do to make amends. Truly innocent people are frequently very remorseful, and try very hard to convince the victim's family that they really are innocent. Mumia has done nothing of the sort.
Ms. Stewart, certainly not a psychopath, thinks she's above the law. Now it may be that the Special Administrative Measures are unconstitutional, or that our government is asserting too much power in the fight against terrorism. But Ms. Stewart's status as a defense attorney does not give her the right to simply ignore these laws. The state depends on competent defense attorneys, and Ms. Stewart is to be commended for her full-throated defense of Mr. Abdel-Rahman. She made the difference between a real trial and a kangaroo court. Nobody has any interest in "railroading" her to jail for defending her client. But it's one thing to defend accused bank robbers in a courtroom; it's quite another to help them rob banks. It's the latter that she is convicted of doing, and for this she deserves to be in jail.
A political prisoner, properly understood, is somebody jailed because of their opposition to the regime. By this measure, neither Mumia Abu-Jamal nor Lynne Stewart are political prisoners. They should not be defended as such.