CAPT OF A CPR PIPER NAVAJO TAXIING OUT FOR TKOF CROSSED A PARALLEL RWY WITHOUT CLRNC DUE TO A MISUNDERSTANDING OF TAXI CLRNC.

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I WAS ACTING PIC AND THE NEW CHIEF PLT WAS WORKING THE RADIOS. WHEN ASKING FOR TAXI INSTRUCTIONS GND CTL ASKED WHICH RWY WE WANTED -- RWY 4L OR RWY 4R. I THOUGHT I TOLD NEW CHIEF PLT I WANTED RWY 4R. I ASSUMED WE GOT A CLRNC TO RWY 4R. I TAXIED UP TO HOLD LINE ON RWY 4L; ASKED PLT WORKING THE RADIO IF HE WAS SURE WE WERE CLRED TO THE R OR L SIDE. HE ASKED TWR AND I THINK THEY SAID CLRED TO THE L SIDE; BUT I CROSSED TO THE R SIDE. THEY MAY HAVE SAID CLRED TO THE R; I'M NOT SURE. IN RETROSPECT; I WAS NOT GIVING THE RADIO MY FULL ATTN. I WAS PREOCCUPIED WITH SETTING UP NAV AND OTHER THINGS IN THE ACFT. I WAS ALSO ON MY FIRST FLT WITH THE NEW CHIEF PLT. I SHOULD HAVE BEEN PAYING EXTRA ATTN TO THE RADIO; ESPECIALLY WITH A NEW PERSON IN THE ACFT. IN THE FUTURE I WILL TAKE MORE TIME AND PAY CLOSER ATTN TO THE RADIO EVEN IF SOMEONE ELSE IS COMMUNICATING. I AM STILL NOT SURE IF WE CROSSED A RWY IN ERROR OR IF WE WERE CLRED ACROSS. NEITHER THE TWR NOR GND CTL SAID ANYTHING; SO PERHAPS WE WERE IN THE RIGHT PLACE. I WILL PAY MUCH CLOSER ATTN IN THE FUTURE.