THE PLT HAD AN INSTRUMENT PLT ACCOMPANY HIM ON THE FLIGHT TO MYRTLE BEACH IN THE EVENT THE WX REQUIRED IFR FOR THE RETURN FLT. WHEN THEY ARRIVED AT MYRTLE BEACH, THE PLT DECIDED THAT THEY WOULD REMAIN OVERNIGHT. AFTER VISITING SOME NIGHT SPOTS AND DOING SOME DRINKING, THE TWO BECAME SEPARATED AND WENT THEIR OWN WAY. THE PLT DECIDED TO RETURN TO CHAPEL HILL. HE FLEW THE ROUTE AT 8,500 FEET. ARRIVING NEAR HIS DESTINATION, HE CONTACTED RALEIGH/DURHAM (RDU) APCH CONT AND WAS CLEARED TO DESCEND AT PLT'S DISCRETION, BUT WAS TOLD TO MAINTAIN VFR. SUBSEQUENTLY, THE AIRPLANE COLLIDED WITH TREES IN INSTRUMENT METEOROLOGICAL CONDITIONS IN A HIGH SPEED DESCENT. INDEPENDENTLY CONDUCTED TOXICOLOGY TESTS INDICATED BLOOD ALCOHOL LEVELS OF 0.10% AND 0.071%. ON THE PILOT'S APPLICATION FOR A MEDICAL CERTIFICATE HE HAD DENIED ANY RECORD OF TRAFFIC CONVICTIONS OR EXCESSIVE DRINKING HABITS. DURING THE INVESTIGATION IT WAS LEARNED THAT THE PILOT HAD BEEN CONVICTED FOR DWI IN JUNE 1987 AND HAD HAD HIS DRIVER LICENSE SUSPENDED FOR 1 YEAR IN JANUARY 1988.