Mayor Rahm Emanuel acknowledged Thursday that Chicago needs more police officers on the street, but he won’t ask taxpayers to foot the bill until he’s certain existing officers are being used effectively.

Toward that end, Emanuel and Police Supt. Garry McCarthy announced plans to shift 200 more sworn officers from desk jobs to street duty and assign them to “area saturation” teams already focusing on the gang violence that now has a face: 15-year-old Hadiya Pendleton. . .