Ken, Hugh is as usual right on target with his statements. While all Civil War prisons were similar in many respects each one was a little different. By in large the difference between Northern and Southern prisons was that Southern prisons usually only held military prisoners however there were exceptions to this rule. Since the topic is about Camp Sumter I can safely state that only Northern military prisoners were held within the prison. There was a little stockade about 300 or so feet from Camp Sumter known as Castle Reed, about the size of a football field. For a couple of months Union Officers were held there I believe it would have been March and a little of April of 1864. After that point the Union Officers were transferred to Camp Oglethorpe in Macon, Georgia. The Confederates did house some of their Confederate guards at Castle Reed who had deserted their post at Camp Sumter. However, the Confederates did not put Confederates in Camp Sumter itself.
Remember the movie "The Horse Soldiers" with John Wayne? While many of the scenes were historically inaccurate one scene was on target in my opinion. Do you remember the local sheriff who had captured two Confederate deserters in the movie and then himself was held as hostage? Confederate deserters were at times held in local jails in the South until they could be turned over to proper authorities. Hugh, was exactly correct in my opinion when he said the South did not have a large issue with bounty jumpers as the North did. Federal prisons however tended to house their own prisoners within the prison itself however, they had their own guards and separate holding facilities and were not mixed in with the regular prison population. I see this at Camp Chase a lot. The Union prisoners at Camp Chase had their own detention area and Camp Chase also had a jail which was separate from the detention areas.
Camp Chase was also a place where Federal prisoners on parole were housed until properly exchanged and they too had their own separate area of being detained. In fact they had their own detention camp for awhile called Camp Lew Wallace about 4 miles from the Camp Chase prison. Some of the paroled prisoners enjoyed what they called "French Leave" which was unauthorized leave to go into town as an example. Those who were caught at times found themselves at the Camp Chase jail. However, only one time have I ever saw a Union prisoner held in the general Confederate population and that was by error. The Union soldier had deserted his command in Kentucky (probably making his way back home) and then was captured by the Confederates and joined the Southern Army rather then to go to a Southern prison however he was captured again by Union troops a few days later. The Confederates at the Camp Chase prison told the Union authorities at Camp Chase what had happened and the galvanized Confederate was put under arrest and then held in the Camp Chase jail under guard and awaited his court-martial. However before his trial began he died and he is now buried as a Confederate in the Camp Chase Confederate Cemetery.
To answer your question directly, Camp Sumter did not hold Confederates of any sort within the prison population itself.
Although this is a little off topic a few days ago, I found out through the 1890 census that over 25 former Union soldiers were held as prisoners at the Ohio State Penitentiary in Columbus, Ohio as having committed civilian crimes of course. A couple of them had been former members of the famous "Iron Brigade" and one of them was from the famous "54th Massachusetts Infantry"