FO OF AN MLG ACR ACFT COPIES THE WRONG SID DEP AND FOLLOWS IT DURING DEP RESULTING IN A TURN AFTER TKOF OPPOSITE TO THAT SPECIFIED AND EXPECTED BY ATC.

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SCHEDULED FLT WAS FROM PHX-LAX. FO TOOK CLRNC FROM CLRNC DELIVERY AND READ BACK INCORRECT DEP (DRAKE VERSUS BUCKEYE). UPON DEP; FO (FLYING) BEGAN TO FLY THE DRAKE DEP OFF RWY 8 (L TURN VERSUS R TURN FOR BUCKEYE DEP). I IMMEDIATELY ASKED 'WHERE ARE WE GOING?' AND 'IS THIS THE CORRECT DEP YOU WERE GIVEN?' FO ANSWERED YES (EMPHATICALLY). I IMMEDIATELY ATTEMPTED TO CONTACT THE DEP CTL TO VERIFY THE DEP; BUT COULD NOT BECAUSE FREQ WAS IN USE CONTINUOUSLY. FINALLY; I GOT DEP CTL AND THEY BEGAN ASKING THE EXACT SAME QUESTIONS I INITIALLY ASKED MY FO PREVIOUSLY. THEY TOLD US TO 'FLY PRESENT HDG AND LEVEL OFF AT 7000 FT (?)' BECAUSE OF TFC COMING IN FROM NE. I LATER DISCOVERED THAT MY FO HAD; DURING PREFLT PLANNING; WRITTEN DOWN THE DRAKE DEP FOR THIS PHX-LAX SEGMENT AND WHEN OBTAINING CLRNC FROM CLRNC DELIVERY; FO IGNORED THE ACTUAL CLRNC GIVEN (BUCKEYE). THIS IS WHAT LED TO THE WRONG DEP FLOWN. I FELT LIKE I HAD TO BELIEVE MY FO WHEN SHE TOLD ME THAT THIS WAS THE CORRECT DEP (EVEN THOUGH IT WAS NOT). I MADE EVERY ATTEMPT TO PRECLUDE ANY CONFLICT BY ASKING TIMELY QUESTIONS TO BOTH MY FO AND DEP CTL. IN INSTANCES LIKE THIS; SERIES OF MISTAKES AND POSSIBLE CORRECTIONS LED TO THE DEVELOPMENT OF THIS SIT. IT'S NEVER TOO LATE TO ALWAYS DOUBLE-CHK EVERYTHING.