THE ACFT CRASHED IN A SLIGHTLY NOSE LOW HIGH VELOCITY IMPACT WITH THE ENG OPERATING AT LOW PWR BY THE SIGNATURES ON THE PROP. THE RADAR PLOT SHOWS THAT THE FLIGHT DESCENDED FROM APRX 15000 FT TO ABOUT 10000 FT IN APRX 1 MINUTE. THE ACFT CONTINUED TO DESCEND IN A HIGH SPEED HIGH RATE OF DESCENT SPIRAL WHICH CHANGED TO A HIGH SPEED STALL JUST PRIOR TO IMPACT AS NDICATED BY GRND CONTACT MARKS AND WRECKAGE CLUES THERE WAS A BROKEN CLOUD DECK AT APRX 4000 FT AGL. FRIENDS OF THE PLT DO NOT BELIEVE THAT HE WOULD HAVE CONSCIOUSLY CLIMBED TO ABOVE 15000 FT WITHOUT OXYGEN, LEADING TO A CONCLUSION OF PLT INCAPACITATION PRIOR TO THE CLIMB AND CRASH. ATTEMPTED CONTROL INPUTS FROM THE WIFE COULD HAVE ALTERED THE ACFT PERFORMANCE AFTER PIC INCAPACITATION. DUE TO THE ACC TRAUMA NO CONCUSIONS WERE DRAWN FROM THE PLTS NREMAINS DURING ATUOPSY. THE FLT PATTERN IS THE MAIN EVIDENCE OF LACK OF PLT INPUT DURING THE FINAL MINUTES OF FLT.