Continuation Part Seven: Discussion of the Amanda Knox/Raffaele Sollecito case

[anglolawyer]

As I understand it, a simplified explanation of mixed-DNA analysis and the problems related to suspect-centric evaluation might be the following:

Suppose a sample is analysed, and it shows peaks at the following numbers:

1, 2, 3, 4, 5, 6, 7, 8, 9

Suppose, just for the sake of this example, that every human being had peaks at four (and only four) numbers. So (for example) I might be 2, 4, 7, 8. You might be 1, 3, 4, 9. And so on.....

Now, if the person conducting the test is asked to make a tentative evaluation of whose DNA is on the sample - but without being given any reference DNA profiles to work with - it's very possible (probable even) that they would say something along the lines of: "It's difficult to make any positive singular matches, since there's clearly such an admixture of profiles that singling out any one contributor would be next to impossible.

But suppose now that the person conducting the test was given the reference sample of a particular individual, together (perhaps) with the information that this individual was a suspect. Suppose that this reference sample was 3, 5, 6, 9.
There is now a very real possibility that the person doing the test might look again at the tested sample, and - consciously or unconsciously - find ways to "match" the suspect to the sample. In this example, the tester might find ways to rationalise that the peaks at 1, 2, 4, 7 and 8 were stutters or other forms of artifact, and that therefore the only genuine contributory peaks were at 3, 5, 6 and 9. And hey presto! Suddenly the tester is able to conclude that the tested sample "matches" the profile of the suspect.

I think I have the driving principles of this issue correct - but anyone should feel free to correct me if I've got any aspect fundamentally wrong. Again, my example is meant to greatly simplify the real-world genetics, in order to highlight the underlying principles.

Suppose 3 5 6 9 were higher peaks than the others?

 

[Grinder]

One last post I was pleased to see that TMB gave false negatives because like you I had been searching. Of course the prints were blood and a belated thank you for the false neg info.

Did you miss the part about luminol hits not being blood? Did you miss the part about the need for a confirming test? Did you miss the part where DNA of Meredith wasn't found?

Stef probably tried to do DNA on the prints and either came up with someone else's or none.

 

[LondonJohn]

One last post I was pleased to see that TMB gave false negatives because like you I had been searching. Of course the prints were blood and a belated thank you for the false neg info.

?

Can I perhaps try to explain to you what sensitivity and specificity mean, and why they are extremely important in the context of testing for blood?

Imagine for a moment that the Luminol test is tantamount to using a "Mammal" test to test for dogs. So, in other words, you have a "thing" that you place into the machine, and it returns a positive or negative result. Let us suppose that this "Mammal" test is infallibly good at detecting a mammal if one is present. This is measure of the test's high sensitivity to mammals.

So you place your "thing" in the machine, and run the test. Remember, you want to find out if the "thing" you're testing is a dog. Now, what can you infer if the test comes back negative? Well, since you know that the test is infallible in finding mammals, and since a dog is a mammal, you can say with certainty that a negative test means you do not have a dog.

But now comes the interesting part: what can you infer if the test comes back positive? Does that tell you that you have a dog? Well, clearly it does not. It tells you nothing more than that you have a mammal. And there are plenty of mammals other than dogs.

This is analogous to getting a positive result in a Luminol test, when you're testing for blood. There's definitely something there that returns a positive with Luminol, but the problem is that there are lots and lots of substances other than blood that also return Luminol positive.

So going back to the analogy, what do you now need to do to prove that the mammal you have is actually a dog (as opposed to an elephant or a mouse or a cat etc.)? Well, you try to find another test that can tell you whether what you have is specifically a dog as opposed to any other sort of mammal. Perhaps this test is not quite as sensitive as the "Mammal" test: in other words, if it comes back negative, there's still a small chance that this is a false negative and that you do in fact have a dog. But that's a trade-off you're prepared to take, because it's still a highly sensitive test in absolute terms, and it also has the key attribute you need: it is highly specific to dogs. In other words, if it comes back positive, you can be pretty certain that what you have is a dog, as opposed to any other mammal.

So you run this second test and it indeed comes back positive. You can now say, with an extremely high degree of confidence, that you have a dog. But if the second test comes back negative, you can be pretty damn sure that you do NOT have a dog: the high probability (on account of the known positive in the first "Mammal" test) is that you have a mammal, but that this mammal is not a dog (on account of the negative in the second test). There is also a small chance that you do actually have a dog, and that the second test has returned a false negative. But the "positive then negative" pair of results is FAR more likely to mean that you have a non-dog mammal.

This is exactly what we have in the Kercher case forensics: we have substances that tested positive with Luminol, but then tested negative with TMB. The huge likelihood from this pair of outcomes is that the substance is something that reacts to Luminol, but which is not blood.

Stefanoni appears to have tried to keep the TMB results secret. If so, that is unforgivably bad scientific misconduct. Negative TMB results essentially invalidate the positive Luminol results. Stefanoni either knew this to be true (in which case she was maliciously trying to deceive) or she was ignorant of this fact (in which case she's not fit to be a lead forensic scientist on a major criminal case). Which alternative do you prefer......?

 

[LondonJohn]

Suppose 3 5 6 9 were higher peaks than the others?

Well, you're now introducing extra complexity into the analogy - something I was trying to avoid in order to illustrate the underlying principles!

But obviously if 3, 5, 6 and 9 were all significantly higher than the rest, the tester would be able to say - without even having seen the reference sample - that a likely contributor to the test sample was an individual with peaks at 3, 5, 6 and 9.

And in any case, in the case of the bra clasp, I think I am correct in saying that the situation is more akin to (for example) 3 and 6 being taller than the rest, and (say) 7 and 8 (i.e. peaks not associated with the reference profile) also being taller. Once the tester has the "3, 5, 6, 9" profile in front of him/her, (s)he might find ways to rationalise away the tall peaks at 7 and 8, and to find a reason why "true" contributory peaks at 5 and 9 might be low.

 

[yimyammer]

Looking at this drawing, four people are going to fight in this room without leaving marks and blood stains everywhere

To me, this is the biggest elephant in the room I never hear mentioned.

How in the heck with all that blood are there not three different footprints in this room?

Additionally, for those that believe the partial foot print among the cluster of prints identified as Rudy's is Amanda's, did Amanda levitate to that location and leave only a single partial print?

How does that happen?

 

[Chris_Halkides]

Quickenden

Grinder,

Luminescence. 2001 Jul-Aug;16(4):295-8.
A study of common interferences with the forensic luminol test for blood.
Quickenden TI1, Creamer JI. link to abstract here

Another false positive is animal blood. One study showed that Draino gave a false positive.

 

[Grinder]

?

Can I perhaps try to explain to you what sensitivity and specificity mean, and why they are extremely important in the context of testing for blood?

Imagine for a moment that the Luminol test is tantamount to using a "Mammal" test to test for dogs. So, in other words, you have a "thing" that you place into the machine, and it returns a positive or negative result. Let us suppose that this "Mammal" test is infallibly good at detecting a mammal if one is present. This is measure of the test's high sensitivity to mammals.

So you place your "thing" in the machine, and run the test. Remember, you want to find out if the "thing" you're testing is a dog. Now, what can you infer if the test comes back negative? Well, since you know that the test is infallible in finding mammals, and since a dog is a mammal, you can say with certainty that a negative test means you do not have a dog.

But now comes the interesting part: what can you infer if the test comes back positive? Does that tell you that you have a dog? Well, clearly it does not. It tells you nothing more than that you have a mammal. And there are plenty of mammals other than dogs.

This is analogous to getting a positive result in a Luminol test, when you're testing for blood. There's definitely something there that returns a positive with Luminol, but the problem is that there are lots and lots of substances other than blood that also return Luminol positive.

So going back to the analogy, what do you now need to do to prove that the mammal you have is actually a dog (as opposed to an elephant or a mouse or a cat etc.)? Well, you try to find another test that can tell you whether what you have is specifically a dog as opposed to any other sort of mammal. Perhaps this test is not quite as sensitive as the "Mammal" test: in other words, if it comes back negative, there's still a small chance that this is a false negative and that you do in fact have a dog. But that's a trade-off you're prepared to take, because it's still a highly sensitive test in absolute terms, and it also has the key attribute you need: it is highly specific to dogs. In other words, if it comes back positive, you can be pretty certain that what you have is a dog, as opposed to any other mammal.

So you run this second test and it indeed comes back positive. You can now say, with an extremely high degree of confidence, that you have a dog. But if the second test comes back negative, you can be pretty damn sure that you do NOT have a dog: the high probability (on account of the known positive in the first "Mammal" test) is that you have a mammal, but that this mammal is not a dog (on account of the negative in the second test). There is also a small chance that you do actually have a dog, and that the second test has returned a false negative. But the "positive then negative" pair of results is FAR more likely to mean that you have a non-dog mammal.

This is exactly what we have in the Kercher case forensics: we have substances that tested positive with Luminol, but then tested negative with TMB. The huge likelihood from this pair of outcomes is that the substance is something that reacts to Luminol, but which is not blood.

Stefanoni appears to have tried to keep the TMB results secret. If so, that is unforgivably bad scientific misconduct. Negative TMB results essentially invalidate the positive Luminol results. Stefanoni either knew this to be true (in which case she was maliciously trying to deceive) or she was ignorant of this fact (in which case she's not fit to be a lead forensic scientist on a major criminal case). Which alternative do you prefer......?

Where “X” is a chromogenic compound (e.g. tetramethylbenzadine-TMB)

A presumptive test, when positive, allows a conclusion that blood maybe present at a crime scene. On the contrary, a negative test may eliminate the need for further consideration. A positive test or negative test though cannot for certain determine that the stain is or is not in fact blood. There are substances such as plants that possess peroxidase-like activity, which could results in a false positive, and by the contrary this reaction could be inhibited by chemicals thus resulting in a false negative

 

[CoulsdonUK]

They haven't been able to examine the EDFs or any of the testing machine's primary source data. Nobody outside of Stefanoni has ever been able to do so.

But they have both examined the electropherograms - that's the most they can possibly have to work with, unless and until Stefanoni provides proper full disclosure. Most informed people realise this will almost certainly never happen. It's likely that Stefanoni has thrown away the vital source data, with a second (but less likely) possibility that she still has the data but is deliberately hiding it from the defence and every other interested party.

Oh okay thanks; so the context of their contribution is that neither of them have seen the EDF’s but they both saw those electropherograms thingybobs; got it.

You guys really need to pitch this stuff for the average woman and man in the street and not the PIP vs. PGP bubble. For me, neither of them saw the necessary evidence.

 

[anglolawyer]

Oh okay thanks; so the context of their contribution is that neither of them have seen the EDF’s but they both saw those electropherograms thingybobs; got it.

You guys really need to pitch this stuff for the average woman and man in the street and not the PIP vs. PGP bubble. For me, neither of them saw the necessary evidence.

Meet them half way, Coulsdon. There are some knowledgeable people posting. You have a chance to interrogate for free. Why not use it to pin them down or learn something?

 

[CoulsdonUK]

Meet them half way, Coulsdon. There are some knowledgeable people posting. You have a chance to interrogate for free. Why not use it to pin them down or learn something?

I am really not having a go at the knowledge of (some) people posting on JREF; nonetheless I believe I make a fair point.

ETA:- Do you really believe the average woman or man with a passing interests in this case would post? I don’t think so!

 

[Bill Williams]

A kind of left field question about the DNA experts that appeared in the BBC 3 TV programme (Balding) and BBC radio 4 programme (Gill); did either of them actually examine anything from the crime scene, it wasn’t clear from either programme?

It’s just that I think it has been mentioned once or twice about the lack of EDF’s being released.

I may be the last person here entitled to comment on this, but this is what they should have said:

They should have said that Stefanoni had a choice with the presumed Meredith trace on the knife blade. Since it was so small of a sample, the sample would be destroyed with one test - since it was a destructive test. She could either test for the owner of the sample, or its composition, not both.

I a move which even I would agree is the only one Stefanoni could make, she chose to test to i.d. who this sample belonged to. It was not good, for instance, to find that it's blood, but not know whose blood it was.

Stefanoni wrote out that she found that the trace belonged to Meredith.

So she reported that as what she found. However, when asked to produce the electronic data files, the raw sample files, she either refused, delayed or outright disobeyed a court order. Without the EDFs, there was no independent way to verify Stefanoni's work.

Further to this, when asked how such a small sample could survive what the cops had called, a thorough scrubbing with bleach, she claimed to have found it in a groove in the blade. No one else can find that groove. DNA is the first thing to be destroyed when bleach cleans stuff... so that's the first hurdle... where the "groove" in which the small sample could have survived the cleaning?

No one can find it. Massei accepted Stefanoni's explanation that she found it by holding the blade under her lab-light and slowly rocking the blade back and forth. Hellmann, obviously, did not. Neither would have I... because so far this is not rocket science, it looks to me to be good old fashioned lying.

Instead, BBC3 just commented on the "abundant amount of DNA evidence" without even describing how Massei made sense of things.... the LCN, etc. The destructive test where the type of substance was unknowable.

I mean, if BBC3 said that Meredith's blood was found on the knife, then that's just a lie - even by Massei's standards.

You see - I have a pet theory that Andrea Vogt, Machiavelli, and BBC3 presented a documentary based on the case Mignini brought to trial; one that tends to mitigate Rudy's involvement.... yes, even the guy whose DNA is found in the victim's vagina.

Neither Massei, nor Crini, nor the ISC (as far as I can tell) really vindicates Mignini; they have moved on to other reasons why they want to find Knox and Sollecito guilty.

I would invite you to lay those other reasons side by side with what you saw in the BBC3 documentary. For some reason Andrea Vogt, the producer, needs to vindicate Mignini's case.... even in the context that Knox and Sollecito stand preliminarily convicted?

Why is that? Why does Mignini need defending?

I think that this is set out to you in a way that is not part of a PIP, PGP polemic. Truly, I'd like someone on that side of the fence to take a shot at answering?

Why would Crini, for instance, 6 years after the fact, start talking about the equivalency of the kitchen knife and the bedsheet outline? Even Mignini did not talk about that? Did Andrea Vogt mention Mignini's two knife theory, precisely because the kitchen knife does-not match the bedsheet outline?

I think the average person can follow this and make up their mind on those matters by themselves.

 

[Bill Williams]

I am really not having a go at the knowledge of (some) people posting on JREF; nonetheless I believe I make a fair point.

ETA:- Do you really believe the average woman or man with a passing interests in this case would post? I don’t think so!

Why not? If someone were to post, "I read in some comments section a knowledgable man say that there was mixed blood on the scene, and that there was abundant DNA of the two accused to convict them," why would you not want them posting that?

 

[CoulsdonUK]

Why not? If someone were to post, "I read in some comments section a knowledgable man say that there was mixed blood on the scene, and that there was abundant DNA of the two accused to convict them," why would you not want them posting that?

Bill

In answer to your post #10752, please refer to post #10751.

Kind of reminds of those Peanut cartoons, Charlie Brown; blah blah blah TOD, blah blah blah timeline, blah blah blah sceptic critical thinking, blah blah blah blah, wolly Mammouth!!

 

[anglolawyer]

I am really not having a go at the knowledge of (some) people posting on JREF; nonetheless I believe I make a fair point.

ETA:- Do you really believe the average woman or man with a passing interests in this case would post? I don’t think so!

I don't think this thread is for the average woman or man. It's for folk who are willing to meet the demands of this complicated case.

 

[acbytesla]

Tesla, did I say that the court should accept that it was blood? No, that is a straw man. What I said was that in my opinion with the testing that we are aware of I don't believe that blood has been eliminated as the source, but that with what we know the prints could have preceded the murder as a weak solution of blood could have survived cleaning if a strong cleaner wasn't used. In that no one has determined what the substance was my speculation gives another option to the ridiculous horseradish or turnip juice thrown out by, what was the term Anglo protested, lame posters.

I have never said you did. It's not really a straw man at all It really is two different arguments. From a purely speculative position. I find nothing wrong with your post at all. It might absolutely be what you suggest. But we will NEVER know that.

The PG have long ago determined that it is Meredith's blood left by Amanda's feet. I'm not the only one that can see the difference in the sensitivities.

So? That doesn't make it or them right. The prosecution and the PGP are arguing that everyone ignore a perfectly valid forensic test because it is inconvenient to their case for guilt. That isn't a good reason.

BTW. I think your argument would be extremely appropriate if Stefanoni had actually performed a third confirmatory test and the result was positive.

 

[CoulsdonUK]

I don't think this thread is for the average woman or man. It's for folk who are willing to meet the demands of this complicated case.

Fair enough. However, doesn’t one need to win the hearts and minds of Mr, Mrs and Ms average in <insert country of choice>?

 

[Bill Williams]

Bill

In answer to your post #10752, please refer to post #10751.

Kind of reminds of those Peanut cartoons, Charlie Brown; blah blah blah TOD, blah blah blah timeline, blah blah blah sceptic critical thinking, blah blah blah blah, wolly Mammouth!!

[QUOT=CoulsdonUk]A kind of left field question about the DNA experts that appeared in the BBC 3 TV programme (Balding) and BBC radio 4 programme (Gill); did either of them actually examine anything from the crime scene, it wasn’t clear from either programme?

It’s just that I think it has been mentioned once or twice about the lack of EDF’s being released.[/QUOTE]

Ok.... they couldn't have tested anything from the "crime scene" strictly speaking. Stefanoni destroyed the bra-clasp and its hook letting it rust, and the lone smidgeon of presumed Meredith DNA on the knife was destroyed due to testing. (I should say *necessarily* destroyed, because it was a destructive test.)

Why does that rate a blah, blah, blah?

 

[Grinder]

Bill

In answer to your post #10752, please refer to post #10751.

Kind of reminds of those Peanut cartoons, Charlie Brown; blah blah blah TOD, blah blah blah timeline, blah blah blah sceptic critical thinking, blah blah blah blah, wolly Mammouth!!

Coulsdon, I think this is what you are talking about

We've gone over this many a time and I don't think this forum will impact the case beyond a small chance a good idea might be passed on by some of the insiders.

 

[LondonJohn]

Fair enough. However, doesn’t one need to win the hearts and minds of Mr, Mrs and Ms average in <insert country of choice>?

Personally speaking, I don't give a damn about "winning hearts and minds". I am not an advocate. I am not even a "supporter" in an active sense of the word. I am someone who finds this subject interesting and who has some opinions on it. I appreciate a forum in which I can debate those opinions, have them challenged, challenge others' opinions, and generally become more well-educated and enlightened about the case.

Aside from my personal motivation, I'd also ask why anyone - even true advocates and partisans - should be overly concerned about any "battle" for hearts and minds, and in particular the hearts and minds of the general public in whatever country. There might be some limited value in trying to convince the genuine decision-makers (courts, politicians etc). But I don't think that this forum (or anywhere else on the internet, for that matter) would be a particularly good means of attempting this. Rather, a forum such as this might be useful in terms of generating ideas/strategies, and "road-testing" them, prior to any approach directly to decision-makers.

As regards the general public, though, I would imagine that the only people who worry about what the general public think would be Knox and Sollecito themselves, and their families and close friends. And they have a far, far better chance of communicating with the general public via either the mass media or their own social networking/blog sites, rather than a rather specialised forum such as this. And in this regard, it would appear that Knox in particular has had a significant degree of success in "winning hearts and minds" of the public in the country which (presumably) matters most to her: her home country of the USA.

 

[acbytesla]

Fair enough. However, doesn't one need to win the hearts and minds of Mr, Mrs and Ms average in <insert country of choice>?

That is the crux of the dilemma. I wonder just how many people just read through this forum with an open mind? It certainly doesn't seem like anyone who actually posts ever changes their minds on the question of guilt or innocence.

You seem like you've been in the same position you were a year or two ago. Maintaining a somewhat pro-guilt position. I've always had hope for you since you seem more reasonable than most of the PGP. That said, I wonder if you have moved an inch.
My goal has always been to persuade everyone, but there is almost a universal truth to this kind of debate. And that is anyone who becomes publicly vested on one side of an argument, never publicly flips their position.

So, is it my goal to to demolish my opponents arguments without mercy so those that are just viewing will easily see the superiority of the argument for innocence. Or alternatively be gentle and try futilely to persuade those that cannot be persuaded.

Should I be Genghis Khan or Don Quixote?