Physical and chemical evidence remaining after the explosion of large improvised bombs. Part 1: Firings of ammonium nitrate/sugar and urea nitrate

Recent criminal acts in the United Kingdom, United States and other countri es have demonstrated the dangers to public safety from the criminal use of improvised explosives on a large scale. Four sets of trials were carried ou t over four years, partly in collaboration with the United States Federal B ureau of Investigation, involving the firing of large bombs, mostly fertili zer based. The principal objectives of the firings were to measure the phys ical effects of the explosions upon objects representative of those that wo uld he found at a real bomb scene and to recover any chemical traces deposi ted on these objects. The results are intended for use as an aid in determi ning the approximate size and type of an explosive employed in a terrorist attack. This paper describes the background behind the trials. the procedur es for preparation of witness materials and charges, and the collection and analysis of physical and chemical evidence.