WITNESSES RPRTD THE ACFT HAD CIRCLED THE AREA 2 TIMES AT APRX 200' BEFORE IT HIT TREES & CRASHED. SUBSEQUENTLY, IT CAME TO REST AGAINST A RESIDENCE WHERE THE PLT'S SISTER LIVED. ACCORDING TO THE PLT, THE ENG STARTED 'SPUTTERING,' SO HE APPLIED CARB HEAT, BUT IT CONTD TO LOSE POWER. HOWEVER, NO PREIMPACT PART FAILURE OR MALFUNCTION WAS FND & WITNESSES RPRTD THE ENG WAS RUNNING NORMALLY BFR IMPACT. THE PAX RPRTD THEY HAD BEEN AT A PARTY THE NGT BFR & HAD BEEN DRINKING & SMOKING 'KOOLS' (COMMON STREET NAME FOR CIGARETTES DIPPED IN PHENCYLIDINE (PCP)). BASED ON THEIR OBSERVATIONS, SHERIFF DEPUTIES BELIEVED THE PLT WAS UNDER THE INFLUENCE OF PCP. THEY NOTED PHYSICAL SYMPTOMS OF DRY MOUTH, DIFFICULTY WITH SPEECH, RIGID BODY MOVEMENTS, HORIZONTAL NYSTAGMUS TO THE EYES & FAINT PCP ODOR EMITTING FROM THE PLT'S BREATH & PERSON.THE DEPUTIES REQUESTED THAT THE PLT SUBMIT TO BLOOD OR URINE SAMPLES FOR DRUG AND/OR ALCOHOL USE; HOWEVER, HE REFUSED.