One of them was literally unconscious as clearly they have been severely roughed up - and likely tortured - by security services. Russian authorities haven't been shy about this considering the number of videos now circulating showing portions of the intense and physical interrogations in action. The maximum penalty is reported to be life imprisonment, though it's likely that torture or continued harsh physical punishment awaits them. According to more details from Russian media:

A Moscow court convened late on Sunday to hear prosecutors' demands on pre-trial detention for a group of men detained in the aftermath of Friday's Crocus City Hall attack, which claimed lives of over 130 people.

The suspects, all of whom are nationals of Tajikistan, appeared individually. Thus far, terrorism charges have been levelled against 32-year-old Dalerdzhon Mirzoyev, who faces a life sentence if found guilty. Prosecutors told Judge Timur Vakhrameev that the suspect had admitted his guilt. 

The court has opted to rule behind closed doors.

Below is what is known of the four thus far, based on statements in Russian media: 

1) Dalerjon Mirzoev - Confessed - 32, Illegal Immigrant from Tajikistan, overstayed work visa, father of 4 young children.

2) Saidakrom Rachabalizoda - 28, allegedly born in Tajikistan, lives in Moscow.

3) Shamsiddin Fariduni - 24, Born in Tajikistan, factory worker, father of an 8-month-old baby.

4) Muhammadsobir Fayzov - Hairdresser, wheeled in on a stretcher to court. All have reportedly been charged under Russia's "Terrorist Act" for their alleged involvement in the Crocus City Hall terrorist attack.