A WITNESS RPRTD THAT DRG TAKEOFF, THE ACFT ROTATED TO A STEEP (NOSE UP) ATTITUDE, & IMMEDIATELY AFTER LIFT-OFF, THE PLT MADE A STEEP LEFT TURN & ENTERED A DOWNWIND FOR LNDG ON THE SAME RWY. HE DESCRIBED THE DOWNWIND AS BEING A LITTLE TIGHTER THAN NORMAL & A LITTLE LOW. HE NOTED A PWR RDCN WHEN THE ACFT WAS ABEAM THE RWY THRESHOLD. RPRTDLY, THE PLT MADEA TURN TO BASE LEG & BGN TO OVERSHOOT THE FINAL APCH PATH. ACCORDING TO THE WITNESS, THE ACFT ENTERED A VERY STEEP BASE TO FINAL TURN, THEN STALLED & BGN TO SPIN. RPRTDLY, THE SPIN STOPPED AFTER APRX 1/2 TURN, BUT THE ACFT STRUCK THE GND BFR THE PLT COULD RECOVER. THE ACFT WAS BADLY DMGD BY IMPACT & FIRE. NO PREIMPACT MECH PROBLEM WAS FND. A TOXICOLOGY RPRT INDCD THE AVAILABLE SPECIMEN OF THE PLT'S BLOOD WAS DILUTED WITH OTR BODY FLUIDS. THE SPECIMEN TESTED POSITIVE FOR ALCOHOL, BUT THE PLT'S BLOOD/ALCOHOL LVL WAS NOT DETERMINED. A TEST OF HIS URINE SHOWED AN ALCOHOL LVL OF 0.256% (256 ML/DL). PHENYLPROPANOLAMINE (A DECONGESTANT) WAS DETECTTED IN HIS URINE, BUT NONE WAS FND IN HIS BLOOD.