B737-800 CAPT PAST THE RWY HOLD SHORT AFTER TURNING OFF RWY AFTER LNDG RESULTING IN THE TWR FILING A PLT DEVIATION.

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I WAS THE FO AND THE PLT NOT FLYING (PNF) DURING THE ABOVE REFERENCED FLT. AFTER APCH AND LNDG ON RWY 25L AT LAX. TWR INSTRUCTED US TO EXIT ON TXWY MIKE AND HOLD SHORT ON RWY 25R. WE RECEIVED THE CLRNC AT APPROXIMATELY 80 KNOTS AND I READ THE CLRNC BACK OVER TWR FREQUENCY. AS THE ACFT EXITED RWY 25L I INITIATED THE AFTER LNDG CHKLIST. AS I WAS COMPLETING MY FLOW I OBSERVED THAT WE WERE CROSSING THE HOLD SHORT LINE FOR RWY 25R. I NOTIFIED THE CAPT THAT WE WERE INSTRUCTED TO HOLD SHORT. HE THEN STOPPED THE ACFT. WE WERE PAST THE HOLD SHORT LINE; BUT I COULD OBSERVE THE RWY EDGE IN FRONT OF THE NOSE OF THE AIRPLANE. AFTER CLRNC FROM TWR TO CROSS RWY 25R WE TAXIED ACROSS AND JOINED TXWY SO WE COULD TAXI TO OUR GATE. DURING TAXI GND NOTIFIED US OF A POSSIBLE RWY INCURSION AND ADVISED US TO CALL THE TWR SUPVR. FOLLOWING THE SHUTDOWN CHKLIST THE CAPT CALLED THE TWR SUPVR. FOLLOWING THE PHONE CALL THE CAPT ADVISED ME THAT THE SUPVR BELIEVED THAT WE HAD CROSSED THE RWY EDGE AND WAS GOING TO FILE A DEVIATION. A CONTRIBUTING FACTOR TO THIS INCIDENT WAS THE SHORT ROLL OUT DISTANCE BETWEEN RWYS AT LAX.