Heck Tate says that the switch blade he has came from a drunk man in town. Is this suspicious in any way? Where else could it have come from?

Heck found the switchblade dropped by Ewell when he attacked Scout. He took the blade away. Boo came armed with a kitchen knife and killed Ewell. By taking the blade out of the equation Heck can claim Ewell was the one with the kitchen knife and, being the drunken sod that he was, fell on it killing himself.