the problem with bombs is that once they've been used, there's not a whole lot of evidence left of how exactly the device was constructed. sure, there's residue from the compounds that can lead to forensic discovery, you can even measure the damage and impressions in materials of known property such as wood and make inferences about the gas expansion rate, and even estimate elemental composition based on the brissance from that factor. you can even study plants in an area that was bombed a long time ago and learn some things about the bombing that went on there through variations between that plants take up of nitrogenated compounds and control group plants (bombs are typically good for soil quality). but as far as the wiring, trigger, fuse, and other details, that stuff gets ruined. was the device triggered when the package was opened? if so, how? was it cardboard wrapped in obnoxious amounts of packing tape, which is what most packages look like? was there a spring loaded string attached to a cardboard flap? these things are basically impossible to determine after the bomb has been used.