THE ACFT CRASHED IN ROLLING TERRAIN MINUS ABOUT 6 FT OF ITS LEFT WING. THIS PORTION OF WING WAS FOUND ABOUT 339 FT EAST OF THE MAIN WRECKAGE. EXAM REVEALED EVIDENCE THAT THE OUTBOARD PORTION OF THE WING SEPARATED IN AN UPWARD AND AFT DIRECTION INDICATIVE OF POSITIVE LOADING IN FLT. A TOXICOLOGY RPT ON THE DECEASED PLT AT FIRST REPTED AN ETHYL ALCOHOL CONTENT OF 0.38% IN A LIVER TISSUE FLUID SAMPLE. THIS WAS LATER CORRECTED TO .038%. THIS PLT HAD RECEIVED A WEATHER BRIEFINGS BY TELEPHONE BUT DID NOT FILE A FLT PLAN. AT 1121 THE ACFT DEPTED CHEYENNE & PROCEEDED NORTHWEST. AT 1146 THE PLT CALLED CHEYENNE APP CONTROL & SAID HE WAS IN CLOUDS & WANTED A VECTOR TO CHEYENNE', AFTER A BRIEF CONVERSATION THE PLT CONTACTED DENVER ARTCC WITH THE SAME MESSAGE EXCEPT FOR DESTINATION. HE WOULD NOW ACCEPT VECTORS TO ANY PLACE OUT OFTHE WX. AS SOON AS THE CONTROLLER GAVE A HEADING THE PLT RADIOED HE WAS IN TROUBLE & THERE WERE NO MORE TRANSMISSIONS. RADAR CONTACT WAS LOST AT 1151. A WITNESS SAID THE WX WAS OVERCAST AND 'I HEARD A HIGH PITCHED WHINE....& A LOUD BANG.'