They would know if Nicedemo was the shooter as soon as they picked him up. They use the reagent test for gumpowder residue ASAP. He probably would not have had time to completely wash off the residue. LE are waiting/pressuring him to 'give up' the shooter. With the amount of time that has passed already, looks like Nicodemo might stand tall. I imagine the family's admin members on the street have passed/received messages to Nicodemo through his visitors in jail. Reassurances passed back and forth, etc. If Nicodemo is cut from the same cloth as Mousie, then as Jiggs would say, "The Philly Mob rides again."