Cross - examination of forensic scientist Stuart Crosby (Trial 1)

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Cross-examination commenced by Mr. Humphries

Q. It’s something of a leap, isn't it, to say that if you find six-millimetre ball bearings years after a device has been set off, that, erm, they’re from the same stock of ball bearings?

A. I understood that the ball bearings that had come from Marland Avenue had been recovered in 1999 and the ball bearings I was looking at the in photograph were also recovered in the 1999.

 

Q. The, erm, if they weren't recovered the same year, would that affect your conclusion?
A. Yes, it probably would I would be even less certain of the findings.

 

Q. You say you “would be even less certain.” Do we take it from that that you are less than certain at the moment, but you would be even more uncertain if it was a different year?
A. As I’ve said in my conclusion, erm, the findings provide limited support for the view that the ball bearings are the same. Erm, I think if there had been a number of years separating the two seizures, I may have actually gone down as far as saying that I couldn't comment on the significance of the findings.

 

Q. Did you in fact have a diameter for the ball bearings from the IED?

A. Erm, only an approximate one as far as I recall from Mr. Ritchie’s statement. I think he measured it at approximately six millimetres.

 

Q. But there was no scale on the photograph that you saw was there?

A. Yes there was on the ones that I saw.

 

Q. Was it the scale that appears on photograph 10, which is just a centimetre scale, or was it better
than that?

A. No, I think it was better than that. As I said, the photographs I examined had the individual components, erm, on them and consequently they were photographed with a more accurate scale with millimetres on it.

 

Q. But not like on page 11 which is individual components with again just the centimetre scale?

A. No, I don't think so.

 

Q. But a minute difference in diameter wouldn't necessarily be apparent, would it, from---
A. Certainly not from the photographs that’s why I’ve, I’ve referred to them as “approximately six millimetres.” I think this is why the weight is more critical in this particular instance.

 

Q. And could ball bearings they don't have to be made of the same metal, do they?

A. Generally speaking, I think they are steel. Otherwise they, erm, they will be, erm, they will not act as ball bearing.

 

Q. Has there been any test of the original ones to see if they are steel?

A. Not to my knowledge, no.

 

Q. Or the ones that you examined?

A. No, for the same reason I couldn't carry out comparisons with the suspected, erm, material from the, erm, explosive device.

 

Q. If they were made from different materials, they could have different densities, could they?

A. Yes.

 

Q. And therefore ball bearings of the same weight would have different diameters?

A. Yes.

 

Q. And ball bearings of the same diameters would have different weights?

A. Yes.

 

Q. By “limited support” do you in effect mean that you cannot rule out that they are the same?

A. Yes, that is, that is one way of putting it. But, erm, in trying to address our findings to the court, we tend to use a verbal scale, erm, of which starts with: ‘inconclusive or I cannot assist the court whether these ball bearings match or not’ right up to ‘conclusive’ which is what I was with the split-shot because I could conclusively say they were different. And there are steps which start with ‘limited’ which is the first step, ‘moderate support’, ‘moderately strong support’, ‘strong support’, ‘very strong support’. And it’s an, an exponential step each one is ten-fold more than the next. So if you have ‘inconclusive’ as 1., then ‘limited is somewhere between a figure of 1 and 10, ‘moderate’ is between 10 and 100 that findings are more likely given my proposition that they are the same.

 

Q. And what is ‘conclusive’ on that protocol?

A. Infinite in effect.

 

Q. Sorry?

A. Infinite in effect. There is no other possibility.

 

Q. No, but I mean, I’m sorry, if you were talking about the scale and it goes up ten-fold each time.

A. It’s, erm, it should still be infinite. But scientifically speaking, erm, if we’re talking about DNA comparison where a lot of this statistics has been done, they do not tend, sorry, they do not have a ‘conclusive’ at the end of their scale, whereas in (inaudible) comparison group---

 

Q. Well what’s one down for ‘conclusive’?

A. Yes.

 

Q. Which is what is one down?

A. ‘Extremely strong.’

 

Q. Right. An ‘extremely strong’ support is what on the scale? A. On the scale? Erm, I don't have them off in my head. Limited, moderate, moderately strong, strong, very strong... basically it’s more than 100,000, possibly even a million.
Q. And we are between 1 and 10?

A. Yes.

 

Q. Well, beyond saying they’re both round, they look similar and they look to be a similar size, is it really any more to it than that?

A. And the compatibly unusual nature of finding ball bearings in those locations.

 

Q. When pedal cyclists maintain their own bicycles, do you expect anyone who does that to have ball bearings? A. Erm, I don't own a bicycle myself, but they will have bearings on them on the wheels I imagine so, yes, they could well have them.

 

Q. And if you’re doing your own maintenance or if you maintain or someone in the family maintains bicycles for the post office, it would be a common thing to have would it not?
A. Possibly, yes.

 

Q. And had you known that the ball bearings that were found came from a post office employee’s house, would that have made a difference as to whether you thought they were a common item and therefore a difference as to whether you could say it was ‘limited support’?
A. No, I would still say that, erm, the occupation of the householder would not affect that conclusion particularly. I would not have the knowledge to know whether post office workers are more likely to have ball bearings in their house than anybody else.

 

Q. So you’d ignore the fact that it may be a cyclist, or a post office worker---

A. Yes, I’m taking---

 

Q. ---or a maintenance person?

A. ---I’m taking those as part of the population that may have ball bearings in their house, therefore it’s not unique to have ball bearings in the house, which if it was would be extremely unusual and I would find that the I would consider the findings far more significant. But by saying that I would not expect to find ball bearings in most households is what I’ve used. But if you choose your population to be people who maintain their bikes, then it would be much less, erm, significant.

 

Q. And had another post office worker’s house been searched around the same time, had six-millimetre ball bearings been found there as well, would it be the same limited support that you’d find that they came from the same stock?

A. Yes, I think it would.

 

Q. Which in fact would mean that anyone who had ball bearings around that time is limited support for the fact that they’re the same stock.

A. As long as they’re the same size, yes---

 

Q. Yes.

A. ---and look in the same condition.

 

Q. But they looked in different condition when you saw them, didn't they? #

A. (No Answer).

 

Q. When you saw the photograph...

A. No, some of the ball bearings from Marland Avenue had been cleaned, others were coated in oil. So some were clean some were oily.

 

Q. And was that the condition they were found in do you know, or was that something that had been done to them before you saw them?

A. I, I can't comment. Erm, those were just the two items as provided to me.
Q. You’re nowhere near sure that they’re the same stock, are you?

A. No.
Q. No. I’ve no further questions. Thank you.