According to South Carolina law, it is illegal to drive a motor vehicle while under the influence of alcohol, drugs, or both to the extent that the driver's ability to drive is impaired.  What this means is that when a person who has been drinking or doing drugs drives a car, if his or her ability to drive is affected because of the drugs or alcohol, he or she will be guilty of driving under the influence. 

The penalty for a first offense DUI is a $400 fine or 48 hours to 30 days in jail. 

A second offense of DUI brings a penalty of $2,100 to $5,100 in fines and 5 days to 1 year in jail. 

For a third offense of DUI, the penalty is $3,800 to $6,300 in fines and 60 days to 3 years in jail. 

Finally, for a fourth offense, the penalty is 1 to 4 years in prison. 

S.C. Code Sections 56-5-2930 and 56-5-2940.