Since my GGrandfather was a prisoner at Point Lookout, I have read extensively about conditions there. I will plead a lack of in depth knowledge as to conditions in other prisons both north and South. There are instances of court martial hearings relative to the shooting of prisoners at Point Lookout, they are documented in the Official Records and may be search for at http://www.ehistory.com/uscw/search/index.cfm
Other instances are through personal memoirs written by ex prisoners after the war...granted our memories are not always accurate.
I certainly agree that there are many wacko sites that have misinformation or pure propaganda, but some have what I consider valid references.
I refer you to this site, although I certainly cannot testify to its political viewpoints of truthfulness. It does reference a couple of memoirs:
http://www.censusdiggins.com/prison_ptlookout.html
Read the Point Lookout prisoner experiences of:
Rev. J. B. Traywick John R. King
Point Lookout, Maryland, located in Saint Mary's County, Maryland on the southern tip of the peninsula was deemed the largest and worst Northern POW camp. Point Lookout was constructed of fourteen foot high wooden walls. These walls surrounded an area of about 40 acres. A walkway surrounded the top of the walls where negro guards walked day and night. It is reported the guards were brutal in their treatment of prisoners. Prisoner, John R. King said; "Two days out of every three we were guarded by a gang of ignorant and cruelsome negroes. Please do not think that I dislike the negroes as a race. Many of them are my friends, but the negroes authority over the white people and the defenceless prisoners suffered at their hands. Numbers of scars were left on the frame work of the closets made by negroes firing at the prisoners. The negro guard was very insolent and delighted in tantalizing the prisoners, for some trifle affair, we were often accused of disobedience and they would say, "Look out, white man, the bottom rail is on top now, so you had better be careful for my gun has been wanting to smoke at you all day!" See more of his story at: Written From Memory by John R. King.

No barracks were ever built. The Confederate soldiers were given tents to sleep in until overcrowding became so bad, there were not even enough tents to go around.

Approximately 50,000 Confederate enlisted men were contained within the walls of Point Lookout Prison Camp during it's operation 1863-1865. Prison capacity was 10,000 but at any given time, there would be between 12,000 and 20,000 soldiers incarcerated there.

The extreme overcrowding, Maryland's freezing temperatures, shortages of firewood for heat, and living in tents took it's toll and many lives were lost due to exposure.

As the water supply became polluted and food rations ran low, prisoners died from disease and starvation. Food was in such short supply, the men were reported to hunt rats as a food source. A prisoner, Rev. J. B. Traywick said; "Our suffering from hunger was indescribable". See more of his story at Treatment of Prisoners - Prison Life at Point Lookout.

Estimates report that over 14,000 prisoners died while imprisoned at Point Lookout but the cemetery is known to hold 3,384 soldiers in a mass grave with no evidence to back up this massive figure. According to history data received from Point Lookout State Park, " Of the 50,000 men held at the Point between 1863 and 1865, nearly 4,000 died. Ironically, however, this death rate of 8 percent was less than half the death rate among soldiers who were in the field with their own armies." As you can see, there seems to be some controversy over the number of deaths at this prison.

The Confederate soldiers' bodies have been moved twice and have found their final resting place in Point Lookout Cemetery.