There are two judicial systems in Iran, the public and the revolutionary. Both are Islamic (all secular law was abolished in 1982) and come under the unelected head of the judiciary–accountable only to the Supreme Leader. 

The public courts deal with criminal, commercial, and family law. The revolutionary courts deal with perceived threats to the Islamic regime. Here there are arbitrary arrests, and often defendants have no access to lawyers or a right of appeal. Charges can be as broad as "propaganda against the regime" or "insulting Islam."  

This court system is frightening for all Iranians, but journalists, human rights defenders, and trade unionists have to be especially wary – as do Christians. For it is to these courts they are brought when arrested. Believers are often charged with "action against the national security."