Explosions 8 Flashcards
What terrorist attack occurred in 1974?
Briefly explain what happened?
Birmingham pub bombings
Two bombs were detonated in Birmingham city centre and a third unexploded bomb was found in Barclays bank
The first major attack on ‘soft target’ in UK mainland
What does a ‘soft target’ refer to?
non-government/non-military
In the Birmingham pub bombings, what was the key in determining the composition/construction of the bombs?
unexploded ‘Barclay’s bomb’ as typically use same composition/construction for all bombs
What was the composition and weight of the bomb from the Birmingham pub bombings?
What were police looking for from this?
bombs composed of Frangex (types of gelignite found in quarries in Rep. Ireland)
20-50% colloidon cotton (nitrocellulose dissolved in alcohol/ether) mixed with nitroglycerin (NG more powerful explosive and NC easier to initiate)
30-40% saltpetre (KNO3)
<15% wood pulp stabiliser (same role as diatomaceous earth in dynamite)
15 kg
police looking for presence of NC
What analytical technique could be used to detect the presence of nitroglycerin?
TEA coupled to GC
very specifically looking for nitro-containing compounds and is very sensitive
How did the investigators try to find the presence of NC in Birmingham pub bombings?
What was the results?
What was the problem with this?
a Griess test used to detect nitrite ions
NaOH releases the nitrite (NO2) ion from nitroglycerine to give a pink colour
(control: repeat test without use of NaOH to rule out any other sources of nitrite sources)
paired with TLC to test to nitroglycerin
positive Griess test and negative TLC
TLC analysis is very imprecise and does not give reliable quantitative results
What conclusion was made from the court in the Birmingham pub bombings?
What was the problems with this?
Dr Skuse claimed there was a 99% chance that two of the men had NG residue on their hands (how has he quantified this?)
He said he used a NaOH solution so weak that would only test positive if the appellants’ hand had been dripping with nitroglycerin - but then said if they had 5g? (not reasonable as it is shock sensitive)
Later discovered that non-illicit sources containing C-NO2, N-NO2 or O-NO2 functionality would give positive result
Nitrocellulose on playing cards Birmingham six were playing with so this gave positive Griess result
Since the Birmingham six in 1974, what are the 7 improvements in analysis and court procedure?
- more focus on sensitivity and specificity of the test
- more controlled environments e.g. clean rooms with HEPA filters and testing conditions
- better recovery of evidence - less contamination and better documentation
- independent testing by another lab (must do same testing and get same result)
- multiple tests to build case more strongly and build corroborative evidence
- less ‘argument from authority’ with regards to expert witnesses
- more standardised approach to analytical evidence presentation in court (greater body of case law related to explosives)
