After a drunk driving accident, it's not only the impaired driver who might face civil liability. Many states have passed some version of a "dram shop" or "social host liability" law, which can be used to hold a drinking establishment or party-thrower liable when a drunk customer or guest causes an accident after being over-served.
Let's say Dale is drunk and he rear-ends Patty's car at a red light. Patty obviously has a personal injury case against Dale. But what if Dale was falling-down drunk at the Third Party Bar, and the bartender kept serving him anyway? In states that have "dram shop" laws, Patty may be able to file a lawsuit against the Third Party Bar. And if Dale was over-served at Homer's house party, in some states Homer could face a lawsuit from Patty too (as long as certain elements are established).