There’s no universal definition when talking about the subject of a political prisoner.
On the other hand, this is mostly defined as an individual who’s imprisoned for his/her political beliefs and activities.
This is true especially to those who are criticizing or opposing the government.
There are Regulations Being Followed
In line with new guidelines that were set by PACE, individual country rapporteurs for PACE have power to make suggestions on who must be declared formally by the state as a political prisoner. Amnesty International are also using the same term in describing any prisoner whose case is associated by political element. This can be either in the act itself, in motivation of prisoner’s act or motivation of authorities in response.
It’s not Right to Call someone a Political Prisoner
As a matter of fact, there are several international organizations that are as much as possible, trying to avoid political prisoner designation as being it is insufficiently objective. To give an example, the Human Rights Watch in most cases prefer using an alternative phrase “human rights defender” in their campaigns.
It is so seldom that a country is going to invoke their own political prisoner designation. Although, making such announcements will damage their integrity and is dubious at the same time.