FLC OF A BA31 STARTED TKOF ROLL PRIOR TO BEING CLRED RESULTING IN A GND CONFLICT WITH A C152 PREVIOUSLY CLRED TO CROSS THE RWY.

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ACR Y; A BA31 JETSTREAM; HAD BEEN HOLDING SHORT OF RWY 19R AT INTXN K FOR APPROX 30 MINS. THEY WERE WAITING FOR A DEP RELEASE FROM SOCAL APCH TMU FOR ARR AT LAX. THE INITIAL COORD WAS THAT THEY COULD WAIT AT THE RWY AND HOPE FOR A POSSIBLE HOLE (DEP RELEASE) 30 MINS IN THE FUTURE -- OR BE ASSIGNED A SPECIFIC DEP WINDOW; WHICH WOULD BE 1 HR IN THE FUTURE. THE CREW ELECTED TO HOLD AT THE RWY AND HOPE FOR A HOLE TO MATERIALIZE. SOCAL TMU EVENTUALLY CALLED BACK WITH A RELEASE OF XX12 VOID AT XY14. AT ABOUT XX10 I TOLD ACR Y 'FULL LENGTH IS AVAILABLE; RWY 19R TAXI INTO POS AND HOLD.' I ANTICIPATED THAT ACR Y WOULD TURN N ON THE RWY AND TAXI FROM K TO THE APCH END OF RWY 19R; A DISTANCE OF 300 FT. THIS IS NOT UNUSUAL FOR THE OP AT SNA. IN THE MEANTIME; I INSTRUCTED A CESSNA 152; WHO WAS STRAIGHT-IN TO RWY 19R; TO CHANGE TO RWY 19L; AND CLRED TO LAND RWY 19L. THE PLT; ON ABOUT 2 MI FINAL AT THIS TIME; ACKNOWLEDGED AND COMPLIED. I KNEW THAT THE C152 PARKED ON THE W SIDE OF ARPT; SO WHEN HE EXITED RWY 19L AT INTXN J (1600 FT S OF APCH END); I INSTRUCTED HIM TO CROSS RWY 19R; KNOWING ACR Y WAS HOLDING IN POS. I DON'T RECALL IF I TOLD HIM TFC WAS HOLDING IN POS. I DID NOT ADVISE ACR Y THAT TFC WAS XING DOWNFIELD. AS THE CESSNA WAS APCHING RWY 19R AT INTXN J; I OBSERVED ACR Y. AT FIRST IT LOOKED AS THOUGH THEY WERE STILL TAXIING INTO POS; THEN I REALIZED I SAW LNDG LIGHTS ON L AND R WINGS ON; AND IT LOOKED LIKE THEY WERE MOVING FORWARD (S IN TKOF DIRECTION). I TOLD THE CESSNA TO 'STOP' 2 OR 3 TIMES. THEN I TOLD ACR Y TO 'STOP' (I DIDN'T SAY CANCEL TKOF CLRNC BECAUSE I NEVER CLRED HIM FOR TKOF). I ALSO TOLD HIM HE WAS INSTRUCTED TO 'TAXI INTO POS AND HOLD.' THE CESSNA ENDED UP ABLE TO STOP SHORT OF RWY 19R EDGE LINE AS BEST I COULD TELL. THE BA31 REDUCED PWR AND ROLLED THROUGH THE INTXN. I HAD HIM TURN OFF THE RWY TO THE R AT H (2500 FT DOWNFIELD).