John Thompson in his autobiography (see more here) talks about his 25 years of slavery in the south. Besides the main theme of the book, the relation between deeds and the sanctions they cause for those who do them, he goes into the evils of the Southern Slave System. He talks about the poor food and the whippings on some plantations; the separations of certain slaves from their families. These things were obviously evil, and I believe Thompson did a good job describing the slave system in general.
In the South, there were many masters who were professed Christians. Many of these masters would argue for the existence of slavery based on Scripture, even though, ironically, their treatment of the slaves was very, very, very un-biblical. In the Old Testament, there were provisions for slavery. However, the slaves sold themselves, and it was a way to pay off their debts, and it only lasted seven years, and at the seventh year, the slave would be released and given farewell presents by the owner. A person couldn’t be kidnapped into slavery, such as what occurred in the Southern slave system for many years, slaves being kidnapped from their homes in Africa and sent across the ocean to slave markets to be auctioned off. Also, the treatment of the slaves in the South directly violated the instructions of the Apostle Paul in Colossians 4:1, which reads:
Masters, give unto your servants that which is just and equal; knowing that ye also have a Master in heaven.
So, though he gave little information of the Southern law system concerning slaves, but you can get the idea that many things were left up to the masters. You get quite vividly the contrast between a good master and a cruel one. You can also tell some things about the slave system in general; it was unfair and cruel to the slaves, who had no protection unless the master gave them that much needed protection.