Where did the bomb come from

Where actually did the C4 used on the victim originate from? Are we absolutely sure it is from UTK armoury? Where is the proof? It must be established in court that explosives (C4) or whatever bomb used on the victim came from UTK armoury and not from other armoury like the army etc. did not the forensics collect evidence from the crime scene? Can it not establish from the remnants what type of explosive was used and where it came from? Can we hang a person without being absolutely sure that he/she actually committed the crime?