AN AIRBORNE POLICE HELI CROSSED OVER A TAXIING ACFT AT A VERY LOW ALT AFTER LCL ATC ASKED THAT THE HELI HOLD FOR DEP TFC.

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I WAS FLYING IN THE POLICE DEPT'S HELI. CAPT WAS GIVEN A TKOF CLRNC BY THE TWR TO PROCEED N BTWN THE RWYS AND REMAIN E OF RWY 35L. ONE AIRPLANE WAS ON FINAL APCH TO RWY 35L; A SECOND AIRPLANE WAS WAITING ON TXWY C AT RWY 35L; AND A THIRD AIRPLANE (B737) WAS TAXIING SBOUND ON TXWY C TOWARDS US AS WE TOOK OFF. THERE WAS A SPACE BTWN THE HOLDING ACFT AND THE B737 AND CAPT PASSED IN FRONT OF THE B737 AS HE DEPARTED. THERE WERE ADDITIONAL ACFT COMING SBOUND ON TXWY C THAT PREVENTED HIM FROM MOVING FURTHER AWAY FROM RWY 35L. AS WE CONTINUED TO CLB WE PASSED OVER AN ACFT THAT HAD JUST TURNED OFF RWY 35L ONTO TXWY T OR G. AT THAT POINT WE WERE AT LEAST 400 FT AGL AND CLBING. IT WAS CAPT'S BELIEF THAT THE CTLR WANTED HIM TO TAKE OFF BEHIND THE HOLDING ACFT AND AVOID OVERFLYING THE B737. THE B737 APPEARED TO SLOW DOWN AS IT SAW US DEPARTING. THERE WAS NO COMMENT FROM THE TWR OR THE B737 DURING THE TKOF. AS WE APCHED TXWY T THE CTLR ASKED US TO HOLD; WHICH PUT US OVER THE TAXIING ACFT. IT IS MY BELIEF THAT THE TWR SHOULD HAVE HELD US UNTIL IT WAS CLR FOR A W DEP OR CAPT SHOULD HAVE CONFIRMED THAT HE WAS CLRED TO DEPART OVER TXWY C. AFTER THE PATROL FLT WAS OVER WE DISCUSSED THE EVENT AND OPTIONS THAT WERE AVAILABLE TO US GIVEN THE CURRENT WIND CONDITIONS. CORRECTIVE ACTION WILL BE TAKEN TO AVOID SIMILAR SITUATION IN THE FUTURE.