B767-300 RWY INCURSION LAX.

Narrative

B767-300 JFK-LAX. FLT; APCH; LNDG (RWY 25L) AND ROLLOUT WERE NORMAL. CAPT TOOK CTL OF THE ACFT AND TURNED OFF AT TXWY M. WE WERE ISSUED INSTRUCTIONS TO HOLD SHORT OF RWY 25R. I ACKNOWLEDGED TO TWR AND THE CAPT ACKNOWLEDGED TO ME. AFTER WE TURNED OFF AND AS WE BEGAN TO SLOW FROM TAXI SPD TO A STOP; I WENT 'HEADS DOWN' BRIEFLY TO INITIATE THE AFTER LNDG CHKLIST FLOW. WHEN I LOOKED UP WE WERE STOPPED AND THE ONLY LINE I SAW AHEAD OF US WAS THE RWY EDGE. I SAID 'WE'RE PAST THE HOLD LINE' TO THE CAPT AS TWR CLRED AN ACFT FOR TKOF ON RWY 25R. CAPT SAID 'CALL THE TWR;' WHICH I IMMEDIATELY DID. TWR CANCELED HIS TKOF CLRNC AND WHEN HE ACKNOWLEDGED WE WERE CLRED ACROSS RWY 25R. WE WERE TOLD LATER HE HAD NOT STARTED HIS TKOF ROLL. FACTOR: RWYS AT LAX ARE VERY CLOSE TOGETHER AND EVEN AN ANGLED TXWY THE HOLD LINE COMES FAST -- IN A LARGE ACFT YOU MAY NOT EVEN FEEL YOUR TAIL IS CLR OF THE RWY. LESSON: EVEN 5 SECONDS HEADS DOWN MAY BE TOO LONG! SUPPLEMENTAL INFO FROM ACN 428213: GND CTL ADVISED US TO CALL THE TWR ON THE PHONE; WHICH WE DID.