THE ACFT WAS ON A NGT CHECK COURIER FLT. DURING ARRIVAL, THE INDICATED AIRSPEED WAS WELL ABOVE THE LEGAL LIMIT OF 250 KTFOR FLT BELOW 10,000 FT. RWY 4R WAS SELECTED FOR LANDING AFTER THE CREW WERE ADVISED THAT THEIR ORIGINAL CHOICE (RWY 11)WAS NOISE SENSITIVE. THEY WERE ADVISED NOT TO DESCEND BELOW 2000 FT UNTIL ON FINAL APCH. THE TURN TO FINAL WAS COMPLETEDABOUT 1 MI FROM THE RWY AT AN ALT OF APRX 700 FT. A STEEP (5 DEG) FINAL APCH WAS FLOWN WITH AN ESTIMATED 1000 FPM RATE OF DESCENT. ON LANDING, THE ACFT BOUNCED, BANKED/TURNED TO THE RGT, THEN IT HIT THE GROUND, RGT WING 1ST & BURNED. AN EXAM OF THE WRECKAGE REVEALED THE ACFT WAS CONFIGURED WITH THE GEAR EXTENDED, THE FLAPS DOWN 20 DEG & THE SPOILERS RETRACTED. NO EVIDENCE OF A PREIMPACT PART FAILURE OR MALFUNCTION WAS FOUND. THE TRIM WAS SET FOR A HVY RGT WING & THE FUEL SWS WERE SET TO X-FEED FUEL. TOX CHECKS SHOWED THAT BOTH PLTS HAD USED OR BEEN EXPOSED TO MARIJUANA & HAD CO2 IN THEIR BLOOD FROM SMOKING; USE OF MEDICATION (PHENYLPROPANOLAMINE) BY COPLT. EVIDENCE OF PSBL FATIGUE/STRESS TO BOTH.