THE ACFT CRASHED IN A FIELD NEXT TO WHERE A FRIEND OF THE PLT WAS BALING HAY. THE PLT HAD CALLED THE FRIEND EARLIER IN THE DAY & ASK THE FRIEND TO GO FLY WITH HIM. JUST PRIOR TO THE ACDNT, THE PLT FLEW OVER & CIRCLED A COUPLE OF TIMES AT LOW ALT. TWO WITNESSES SAW THE ACFT GO DOWN, BUT THEY COULD NOT BE FND LATER FOR INTERVIEW. AN EXAM OF THE ACFT REVEALED IT HAD CRASHED IN A STEEP NOSE DOWN ATTITUDE. THERE WAS LITTLE MOVEMENT OF THE ACFT AFTER IMPACT, BUT IT WAS RELATIVELY INTACT. NO PREIMPACT MECHANICAL PROBLEM WAS EVIDENT. A HAMILTON COUNTY BLOOD ANALYSIS SHOWED THE PLT HAD AN ALCOHOL LVL OF 20 MG% (0.02%), A COCAINE LVL OF 20 MG% & A DIAZEPAM (VALIUM) LVL OF 10 MG%. TOXICOLOGY TESTS AT THE FAA MEDICAL CENTER SHOWED THE ALCOHOL LVL OF THE PLT'S BLOOD WAS 0.035%, URINE WAS 0.038% & GASTRIC FLUID WAS 0.314%; HOWEVER, TESTS FOR DRUGS WERE NEGATIVE. THE ACFT WAS NOT EQUIPPED WITH SHOULDER HARNESSES.