THE OWNER OF THE HOME BUILT ACFT HAD PURCHASED IT FROM THE BUILDER. HE POSSESSED NEITHER AN FAA MEDICAL, NOR A PLT CERTIFICATE, & HAD NO PREVIOUS FLT TIME IN THIS MAKE & MODEL OF ACFT. HE TOLD A WITNESS THAT HE INTENDED TO TAXI IT (PRESUMABLY FOR FAMILIARIZATION). SUBSEQUENTLY, THE ACFT BECAME AIRBORNE & REMAINED WITHIN ABOUT 1/2 MI OF THE DEP END OF RWY 30. WITNESSES OBSERVED IT MANEUVERING ERRATICALLY AFTER TAKEOFF. ONE WITNESS BELIEVED THE UNQUALIFIED PLT CROSS- CONTROLLED THE ACFT WITH LEFT RUDDER & RGT AILERON; THE WITNESS SAID THE ACFT NEARLY HIT A HANGAR. SUBSEQUENTLY, AFTER AN APPARENT PWR REDUCTION, THE ACFT ENTERED A STALL/SPIN & CRASHED IN A STEEP NOSE DOWN ATTITUDE. A LOCAL CFI RPRTD HE HAD GIVEN THE PLT APRX 4 HRS OF DUAL INSTRUCTION DURING A PREVIOUS 12 TO 24 MONTH PERIOD, BUT THE PLT HAD NOT SHOWN INTEREST IN FOLLOWING A REGULAR/STRUCTURED PROGRAM OF INSTRUCTION. DURING TESTS, CANNABINOIDS WERE DETECTED IN THE PLT'S URINE, BUT NONE WAS FOUND IN HIS BLOOD.