A political prisoner is someone held in prison or other types of confinement such as in the military or a mental institution because their ideas are deemed by an authority to either challenge or threaten the state. A political prisoner may be a prisoner of conscience, deprived of freedom of speech.
Often, political prisoners are imprisoned with no legal veneer directly through extrajudicial processes.
It isn't uncommon for political prisoners to be arrested and tried with a veneer of legality, where false criminal charges, manufactured evidence, and unfair trials are used to disguise the fact that an individual is a political prisoner. This is common in situations which may otherwise be decried nationally and internationally as a human rights violation and suppression of a political dissident.
A political prisoner can also be someone that has been denied bail unfairly, denied parole when it would reasonably have been given to a prisoner charged with a comparable crime, or special powers may be invoked by the judiciary.
Particularly in this latter situation, whether an individual is regarded as a political prisoner may depend upon subjective political perspective or interpretation of the evidence.