Response to Bubu Bubu regarding bullet PV20

[Erik Narramore]

On the Blue Forum, Bubu Bubu posted this regarding PV20:

PV20 analysis as promised
     
                                   BULLET WEIGHT CALCULATIONS             
                   
                     
A                 B              C = B div by A              D           E = C x D         F         G = F div C
Grams      Grains       Grains per gram      Weight given     Grains           Grain    Grams
Eley Data   Eley Data         Ratio             by Taylor gms    per type        weight     per type
                                                                                                        Pv20     
                     
2.59          40              15.4440                 1.5453           23.865637      26.46   1.713285
                   
2.27          35              15.4185                 1.5453           23.826211      26.46   1.71612
                     
1.88          29              15.4255                 1.5453           23.837074      26.46   1.715337931
                   
2.43          37.5           15.4321                 1.5453           23.847222      26.46   1.714608                   
     
PV20 data
                                   
1.5453     26.46          17.1229


                                                  Proving PV20 was swapped.

The figures shown in the table is an analysis of PV20 comparing it to known weight and grain information for all sizes of the .22 hollow point bullet types Ely manufacture. I have created a 37.5 grain type using the averages of the others.

The gram to grain ratio for PV20 should be between 15.4185 and 15.4440. It does not fit with a ratio of 17.1229.

If was weighed by Taylor as 1.5453 grams. It grain weight should be between 23.826211 and 23.865637 grains. It does not compare with a weight by MF of 26.46 grains

If it was 26.46 grains as per MF its gram weight should be between 1.713285 and 1.71612 grams. Once again it does not compare.

The PV20 weighed by Taylor at 1.5453 grams has been swapped by MF because it had incompatible lans and grooves to have been fired by the Anschutz.

Unless the gram to grain ratio changes with fragmentation PV20 is not the same as the fragment weighed by Taylor. It would have to have been swapped.

Grams to grain ratios do vary but are all between 15.41 and 15.44. The ratio for PV20 is 17.122.
I do not know how Jeremy's ballistics expert (was it Major Mead) verified the bullets. Did he reweigh them? Did he convert grams to grains and vice versa? Did he compare information against GERs and other documents? Also what use did he make of the document which describes PV20 as whole where only the 29 grain figures produce a result which might be considered whole? Even without detailed calculations it would be clear to an expert that 26.46 grains was not a whole bullet.

Mead and particularly Fletcher have a lot of questions to answer
.
The CT need to revisit the ballistics data to check for any other incidents of 'Jiggery Pokery'
.
You might want to run this past NGB

Source thread: https://jeremybamberforum.co.uk/index.php/topic,10645.msg494060.html#msg494060

My response to Bubu Bubu:

Could you provide a source for your data and explain what other bullets are being referred to? If these are your own calculations, then please tell us where you obtained the data on which you based your calculations.

Your column C does not make sense to me as mass ratios should be identical.  I suspect the problem is that you, or whoever put the core data together, has rounded-up the imperial mass for each bullet in column B, resulting in a variable mass ratio.  If that were sorted out, then I would expect the mass ratios in column C to be the same.  In both ISU convention and physical reality, 1 gram has to be 15.4323584 grains.  It can't be any other and must always be this, regardless of what happens to any of the bullets.

I agree that the figures in columns A and B for PV20 appear to be out-of-sync, which suggests an issue.  It should be 23.8476234 grains, but unless we know where these figures are from and can see the source, then I'm not sure anybody can usefully comment.

Column D also makes no sense.  You've lost me completely at that point.  The forensic examiner would not come back with the exact same measurement of mass for every bullet.

[Erik Narramore]

Bubu Bubu isn't making himself clear and his table doesn't make any sense to me mathematically.

We need the source document or link to the document or for Bubu Bubu to tell us what document he has seen so we can find it.  It's just convention.

As to what Bubu Bubu is trying to do here, I have to read between the lines, as he's not being clear.  I think what he's saying is that he has transposed the mass recorded for PV20 to columns D and F and multiplied the imperial mass by the varying mass ratios in the hope of finding a bullet that matches the recorded measurements for PV20.

The problem, as I have explained, is that column C is wrong because the mass ratios can't vary.  This means the whole exercise is misconceived.  Column C must always be the same figure common to all bullets.  This means that in column C you are always multiplying by 15.4323584, which in turn means that the product in column G for any bullet will only be the same as PV20 if that bullet has the same mass as PV20 in the first place, which should be self-evident from the source data anyway.

[Erik Narramore]

Bubu Bubu replied with a post that included this sentence:

Similarly 1.5453 grams translates to 23.84762344 grains but MF weighed it at 26.46 grains

I regard this as crucial.  I don't know what Bubu Bubu's source is for Fletcher's measurements, but for the purposes of this discussion, let's take your data at face value and go from there.

I assume it must have been FSS procedure to take two measurements for completeness: one imperial, one metric.  The question is: Why is the recorded imperial measurement of mass inconsistent with the metric measurement for the same bullet?  The laws of physics tell us that the mass ratio is constant and so the measurements have to be consistent to the ratio.

The answer to the question is complex because before we jump into exploring malevolent motives, we first have to consider the possibility of mistake: specifically, in this case, the problem of calibration.  One troy grain is significantly less than a gram.  A gram is roughly the mass of a paperclip.  It's not difficult to see how a mistake could be made, but the likelihood of a calibration error, or even a simple human error in measuring, depends on the measuring instruments used.

We need to see Bubu Bubu's documentary sources and we need to see when the two measurements were taken, what record Fletcher and Taylor made of the instruments they used, how they used them, and how they calibrated these measuring instruments.

[Erik Narramore]

When people take scientific measurements, they are supposed to record the instruments they used and the calibration procedures undertaken.  This is nothing more than conventional method in a range of industries, and I know for a fact it is also the case in forensic science.  Instrument interrogation is every bit as important as the findings and it is supposed to be done and recorded.  I say 'supposed to' because they won't always, and I don't know if it happened here.

Calibration and human error are very relevant considerations before we jump off the deep end accusing people of malpractice.  My experience is in the railways, construction and renovation industries.  Among other things, I have been a track inspector and a site manager.  Instrument calibration is fundamental and anybody who doesn't understand it will quickly fall into error and incompetence.  A simple tape measure, for instance, is actually quite a difficult tool to use in the wrong hands.

[Erik Narramore]

Bubu Bubu proceeded to attach an FSS document that confirms the metric mass of PV20, but it isn't the one that addresses the key point.  Bubu Bubu is saying that Fletcher measured PV20 at 26.46 grains, so I would be interested to see the document that states that, especially if it also shows what measuring instruments he was using.

Also, the document Bubu Bubu provides is giving the 'weight' (should say mass) of PV20 after it is 'spent'.  We know from the notes of Vanezis that the bullet was fragmented.  This leads me to ask: What is the mass in the Eley data for that type of bullet?

[Erik Narramore]

Mike Teskowitz then attached a photograph in the thread taken by Major Mead, the defence ballistics expert that gives the mass of PV20 as 26.46 grains.  I asked if that was put together by Mead or did he simply photograph what he found?  Did he take photographs of the other spent bullets in a similar way?  No response was received from Mike.

[Erik Narramore]

The significance of all this:

If Malcolm Fletcher mismeasured the mass of a bullet, that is an error and of no particular significance in itself.  But if it can be shown that it was unlikely he could have made such an error, then that is of potential significance.

As always, more information is needed before anybody can come to one conclusion or the other.  At the moment, I feel like a moderate trapped between two extreme camps, each of which has a tendency to jump to emotionally-appealing conclusions before all the facts are in.

[Erik Narramore]

People who have not worked in technical jobs may have difficulty appreciating how common it is to come across human error and other things for which there is no clear explanation, or how even the tiniest human error can have significant ramifications.

Measuring errors are, by definition, due to human error, and one underlying factor in this is the operator forgetting to calibrate the measuring tool or not understanding how to use it correctly.  As a practical exercise, find an old tape measure and try measuring a length of anything from the true zero mark, then measure the same thing from the 10 cm. point.  If it's a used tape measure, you'll normally find that the measurements differ - sometimes quite significantly.

Importantly, arguments from mistake do not close the door to Jeremy's pleas of innocence.

[Erik Narramore]

The position remains confused because Bubu Bubu's calculations are wrong as he's not realised that mass ratios of bullets are constant and that Eley were producing rounded-up figures for grain weights.  To carry out the comparison attempted, it is enough simply to check for other bullets commonly-available at the time (not just Eley) that had the same notional weight.

But this raises a further question: if the police really did shoot Sheila and for some reason decided they needed to cover up the fact, wouldn't they have simply swopped out their own bullet for one of the bullets from a cartridge in the house?  If they had time to think about what they were doing, surely that is how they would have gone about it?  They could have spent the bullet during forensic examination.