I got in a fight in a jail cell after being arrested for DUI, I got charged with assault. I posted bail. How serious is this? Will I do time?
Get a lawyer.
Not. really. Probably a ticket; 30 days in the hole. Only assault with GBH or worse is even brought to a proper trial on the inside. Most assaults never get anywhere. Mine was only because CO's noticed a black eye. Took my picture, asked questions. I said., we were playing Pinochle; it's a rough game. That was All. Another I/M hit a steel post while exercising and had a bruise; he got treated like he had been in a fight, too.
Your only POSSIBLE defense for the assault is claiming you were defending yourself from an attack. I suspect the witnesses include at least one guard.
you will be raped in the Medium Security prison they will put you in