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

[Chris_Halkides]

Combur strips from Roche and the Conti Vecchiotti report

Although Luminol is more sensitive than TMB, TMB can detect blood that has been diluted up to 10,000-fold.

10,000-fold is the lower bound for sensitivities that I have been able to find for TMB, and 1,000,000-fold is the upper bound. Conti and Vecchiotti used a version of the TMB test called the Combur test E. with a sensitivity of about 1 part in 400,000. The report states, "Recently, reagent strips (Combur Test) were introduced into laboratory practice: [the strips are] impregnated with organic hydroperoxide and tetramethylbenzidine as a colourmetric indicator; if haemoglobin is present, causing oxidation, [the strips] turn from yellow to green-blue. The test is quick and easy to carry out, and the sensitivity varies, according to the Authors, from 1:300,000 to 1:500,000. False positives are known due to the presence of oxidants (e.g. metals like copper and iron), vegetable or animal peroxidases etc, while false negatives [can occur] due to strong reductive substances (e.g. cyanide) inhibiting the action of the haemoglobin."

EDT
There is a paper that deals with false negatives, namely, Castello et al., Journal of the Canadian Society of Forensic Science, 35(3), 2002, 113-121. They used ascorbic acid and showed that luminol has a higher resistance to interference from ascorbic acid than other presumptive tests, but they only show their luminol results in an earlier study. The results for other presumptive tests are in an earlier paper. Ascorbic acid is a component of lemon juice. So maybe the reason why the TMB tests were negative was because the stains had lemon juice, but Comodi ruled out the possibility of fruit juice on the basis of common sense (J/K).

 

[Kaosium]

Another lie you are going on repeating. The truth: they (Stefanoni?) were never "caught". The TMB tests were revealed by the prosecution themselves.

When?

Even the very existence of the SAL was declared by Comodi first, before anyone ever "caught" her. She was the first one who talked about SALs and laboratory documentation before Massei, not the defence.

Did she say the SAL recorded a negative TMB result? Did she reveal that information while she was contending the luminol hits were made in blood?

Had they wanted to hide the SALs, they would have gone on hiding them, destroy them (like the Carabinieri do with their laboratory items) or would have provided a manifactured SAL.

Of course if they did that and it was apparent that the tests had been done from the video as you suggested the last time this came up, they'd have been in a world of trouble. Plus of course it's standard practice to verify a luminol hit with a TMB test, not just with ILE but many agencies as well, including the FBI, so it would be expected that those tests were done.

Instead, when requested, they gave information without objecting.

When?

So, they were not "caught". They disclosed information (which the defence could have already had, if their experts accessed the laboratories during the investigation), then they disclosed further information on request.

Perhaps they were foolish enough to think the prosecution would honor discovery and not try to misrepresent the evidence they had, which is what they did when they tried to contend blood for a substance which tested negative for blood without revealing that.

Thus, they never hid anything.
I understand you don't like this wording.
But it's the truth.

I know what it is, and 'truth' is not the word I'd employ.

There isn't any 'original contention' and anyway it doesn't matter: there is just a piece of evidence, a series of bare foot shaped luminol stains, which are logically attributable only to stepping in diluted blood after a clean up of the murder scene. While there is no alternative substance nor alternative scenario proposed to explain them.
And this, is absolutely not nonsense. It's logic.

No, it's not.

There's almost an infinite number of things those luminol hits could be and it is far more probable they are not evidence of someone stepping in with bare feet in diluted blood after a clean up of the murder scene. There's little reason to think that they were blood, and if there was blood present (meaning as just part of an overlaying substance on another stain) there's many ways it might have gotten there considering the number of people walking over blood traces and even if they were totally all diluted blood the same dynamic as previously could cause them to be diluted blood made from blood traces getting into moisture being as there's no evidence of a clean up outside crap like this and other indications of a clean-up were it to have happened are missing.

If you believe there is nothing incriminating in diluted blood being in that hallway in that set of prints, in my opinion your contention is something logically impossible to sustain. There isn't a plausible, or probable, alternative explanation for having that specific set of diluted footrpints produced by a totally innocent cause.

You can't prove they are all footprints, you can't prove who they belonged to if they were, you can't prove they were made at the same time, you got a falsifier that they were blood and even if they were there's nothing about these blood traces outside the bathroom that incriminate anyone specifically of being involved in the murder considering all the people that walked over it after the murder.

 

[Skind]

In dear old Machiavelli's world, the following exchange counts as the negative TMB results being "revealed by the prosecution themselves" (I paraphrase......):

The thin Mach is missing out on is simple:

revealing something doesn't mean you weren't hiding it.

Anyone who is hiding something can only have it found out by either being forced to reveal it, having it taken off them and then revealed, or by choosing a strategic point to reveal it. Hiding does not require that you make every endevour to always hide it by any means - there will be a time when it's in your best interests to stop hiding it.

Revealing it does not - cannot - logically mean you were never hiding it.

Mach's definition of 'hiding' could have got prosecution into a heck of a lot of trouble, whereas passive-aggresive tactics allow the prosecution to simply say "Well, they didn't ask for it".

No prizes for guessing what the actual observable behaviour of the prosecution was, and which option it is compatible with.

 

[acbytesla]

False negatives on TMB tests are documented by literature. Even on stains that were revealed to luminol. This is not 'absurd', is simply documented in literature, which I had cited in the past (I actually posted twice abot it).
The 1/10:000 dilution detection is theoretical: in practice, TMB test is indirect (not on the stin but on the swab) and produces a further dlution within the swab itself; we can reasonably speculate it is extremely unlikely that TMB would detect a latent stain above a magnitude of a 1:1000 dilution, but anyway calculation would make little sence since the swab reacts to the absolute amount that it absorbes, not to a concentration.

The problem of course is the lack of confirmatory test. Because Luminol presents countless false positives as well. The fact is there are lots more false positives from Luminol than false negatives from TMB. It would be totally outside standard forensic protocol to come to the conclusion that it is blood with a negative TMB test without the confirmatory test. IN FACT IT WOULD BE WRONG!!! Stefanoni didn't perform the TMB tests without reason. Or do you think she did this, just because? She did it to confirm the Luminol results, had they returned positive, the protocol is then to perform a confirmatory blood test.

Also, the negative TMB test in conjunction with with the fairly clear Luminol footprints and lack of smearing as well as Rudy's clear to the naked eye bloody shoe prints absolutely puts the hammer to the idea that this is blood from the murder.

At what point do you come to a LOGICAL CONCLUSION Machiavelli and stop arguing for arguing sake? You are clearly smarter than this?

My father use to tell me to engage my brain before my mouth. Maybe you should take a moment before your fingers strike another key?

Just maybe?

 

[LondonJohn]

10,000-fold is the lower bound for sensitivities that I have been able to find for TMB, and 1,000,000-fold is the upper bound. Conti and Vecchiotti used a version of the TMB test called the Combur test E. with a sensitivity of about 1 part in 400,000. The report states, "Recently, reagent strips (Combur Test) were introduced into laboratory practice: [the strips are] impregnated with organic hydroperoxide and tetramethylbenzidine as a colourmetric indicator; if haemoglobin is present, causing oxidation, [the strips] turn from yellow to green-blue. The test is quick and easy to carry out, and the sensitivity varies, according to the Authors, from 1:300,000 to 1:500,000. False positives are known due to the presence of oxidants (e.g. metals like copper and iron), vegetable or animal peroxidases etc, while false negatives [can occur] due to strong reductive substances (e.g. cyanide) inhibiting the action of the haemoglobin."

EDT
There is a paper that deals with false negatives, namely, Castello et al., Journal of the Canadian Society of Forensic Science, 35(3), 2002, 113-121. They used ascorbic acid and showed that luminol has a higher resistance to interference from ascorbic acid than other presumptive tests, but they only show their luminol results in an earlier study. The results for other presumptive tests are in an earlier paper. Ascorbic acid is a component of lemon juice. So maybe the reason why the TMB tests were negative was because the stains had lemon juice, but Comodi ruled out the possibility of fruit juice on the basis of common sense (J/K).

Eeek! I think there's some confusion brewing over the term "sensitivity". In binary-classification statistical analysis (e.g. whether a test indicates either positive or negative, and nothing in-between), sensitivity has a very particular meaning, which has nothing to do with the dilution level of the substance being tested.

In this context, "sensitivity" means the ratio of false negatives (or, equivalently, it's a representation of true positives). In other words, for example, if there was a test for (say) malaria that had a sensitivity of 1:20,000, that would mean that - on average - if you took 20,000 people who actually did have malaria, this test would produce a false negative for one of them.

Therefore, when the TMB test is reported as having a sensitivity of 1:300,000, this doesn't mean that it can detect blood diluted down to one part in 300,000. Rather, it means that 1 per 300,000 true blood samples will produce a negative result from a TMB test.

The measure that sits alongside sensitivity is specificity, which is the ratio of false positives (or true negatives). Specificity indicates the proportion of true negative samples that will test as false positives. In the hypothetical malaria test example, if this test had a specificity of 1:500, this would mean that (on average) if 500 people who did NOT have malaria were to be tested using this test, one would produce a false positive result.

I might suggest that the very term "sensitivity" should no longer be employed if it's referring to the dilution of the blood being tested - or, for that matter, if it's referring to the smallest number of erythrocytes necessary to produce a positive result. Both of these definitions are very different from the statistical meaning of "sensitivity" - and it's this statistical meaning that is usually the one employed in scientific reports and journals.

 

[acbytesla]

Eeek! I think there's some confusion brewing over the term "sensitivity". In binary-classification statistical analysis (e.g. whether a test indicates either positive or negative, and nothing in-between), sensitivity has a very particular meaning, which has nothing to do with the dilution level of the substance being tested.

In this context, "sensitivity" means the ratio of false negatives (or, equivalently, it's a representation of true positives). In other words, for example, if there was a test for (say) malaria that had a sensitivity of 1:20,000, that would mean that - on average - if you took 20,000 people who actually did have malaria, this test would produce a false negative for one of them.

Therefore, when the TMB test is reported as having a sensitivity of 1:300,000, this doesn't mean that it can detect blood diluted down to one part in 300,000. Rather, it means that 1 per 300,000 true blood samples will produce a negative result from a TMB test.

The measure that sits alongside sensitivity is specificity, which is the ratio of false positives (or true negatives). Specificity indicates the proportion of true negative samples that will test as false positives. In the hypothetical malaria test example, if this test had a specificity of 1:500, this would mean that (on average) if 500 people who did NOT have malaria were to be tested using this test, one would produce a false positive result.

I might suggest that the very term "sensitivity" should no longer be employed if it's referring to the dilution of the blood being tested - or, for that matter, if it's referring to the smallest number of erythrocytes necessary to produce a positive result. Both of these definitions are very different from the statistical meaning of "sensitivity" - and it's this statistical meaning that is usually the one employed in scientific reports and journals.

This argument is so intellectually dishonest, I would love to go over to Italy and kick some of these bastards in the teeth. Of course I won't do that. The only reason that they are making this silly argument is that means they are losing another possibly incriminating piece of evidence. If the result was that it was somehow incriminating, they would argue the opposite.

I wonder how these people look themselves in the mirror? Machiavelli??

 

[LondonJohn]

Incidentally, sensitivity and specificity issues are the man reason why people being tested for HIV (qv Knox in prison) are not confirmed as HIV+ until two different tests have been conducted on their blood sample. This is because one of the tests has high sensitivity but low specificity, while the other test has both high sensitivity and high specificity.

It's very difficult and expensive to devise a test that has both high sensitivity and high specificity. Normally, one has to be sacrificed in favour of the other. And it's for this reason that two tests in partnership are used for confirmation of a true positive in HIV tests - the first, cheaper, test eliminates the bulk of the true negatives quickly and cheaply, meaning that the second, more expensive and more time-consuming tests only needs to be performed on a much smaller subset of total samples.

The way it works is like this: the first test, known as an ELISA test (which is by far the quicker and cheaper test) is the one that has high sensitivity but low specificity. That means that if you DO actually have HIV, you are extremely unlikely to test negative (i.e. high sensitivity, = low proportion of false negatives). That's a very good thing, since you obviously don't want to be telling people with HIV that they are all clear.

However, this test also has a low specificity. That means that it has a relatively high proportion of false positives. That means that quite a few people who DO NOT have HIV will test as positive with this first test.

Therefore, the outcome of this first test is that anyone who tests negative will almost certainly NOT be HIV positive, and can immediately be informed of this test, with no further testing necessary. But of those who test positive, some will truly be HIV+, but a significant proportion will not (the proportion is directly related to the risk profile of the person being tested, but that's peripheral to this discussion).

That's why, after the first test, people should NOT be told that they are HIV positive. Instead, two things should happen: firstly, all those who test positive should be told that there's a chance they might be HIV+, but that a second test is needed to show whether they really do have HIV. And secondly, their blood sample should be subjected to the second HIV test - the one which has high sensitivity and high specificity.

In this second test, know as Western Blot (which is far more costly and time-consuming than the first), the situation is as follows: if you DO NOT have HIV, you are very unlikely to test false positive in this second test (high specificity); and if you DO have HIV, you are very unlikely to test false negative (high sensitivity).

Therefore, if you test negative in the first test you almost certainly are not HIV+ (and no further test is necessary). If you test positive in the first test and negative in the second test, you almost certainly are not HIV+. Conversely, if you test positive in both the first and second tests, you almost certainly ARE HIV+.

 

[acbytesla]

Incidentally, sensitivity and specificity issues are the man reason why people being tested for HIV (qv Knox in prison) are not confirmed as HIV+ until two different tests have been conducted on their blood sample. This is because one of the tests has high sensitivity but low specificity, while the other test has both high sensitivity and high specificity.

It's very difficult and expensive to devise a test that has both high sensitivity and high specificity. Normally, one has to be sacrificed in favour of the other. And it's for this reason that two tests in partnership are used for confirmation of a true positive in HIV tests - the first, cheaper, test eliminates the bulk of the true negatives quickly and cheaply, meaning that the second, more expensive and more time-consuming tests only needs to be performed on a much smaller subset of total samples.

The way it works is like this: the first test, known as an ELISA test (which is by far the quicker and cheaper test) is the one that has high sensitivity but low specificity. That means that if you DO actually have HIV, you are extremely unlikely to test negative (i.e. high sensitivity, = low proportion of false negatives). That's a very good thing, since you obviously don't want to be telling people with HIV that they are all clear.

However, this test also has a low specificity. That means that it has a relatively high proportion of false positives. That means that quite a few people who DO NOT have HIV will test as positive with this first test.

Therefore, the outcome of this first test is that anyone who tests negative will almost certainly NOT be HIV positive, and can immediately be informed of this test, with no further testing necessary. But of those who test positive, some will truly be HIV+, but a significant proportion will not (the proportion is directly related to the risk profile of the person being tested, but that's peripheral to this discussion).

That's why, after the first test, people should NOT be told that they are HIV positive. Instead, two things should happen: firstly, all those who test positive should be told that there's a chance they might be HIV+, but that a second test is needed to show whether they really do have HIV. And secondly, their blood sample should be subjected to the second HIV test - the one which has high sensitivity and high specificity.

In this second test, know as Western Blot (which is far more costly and time-consuming than the first), the situation is as follows: if you DO NOT have HIV, you are very unlikely to test false positive in this second test (high specificity); and if you DO have HIV, you are very unlikely to test false negative (high sensitivity).

Therefore, if you test negative in the first test you almost certainly are not HIV+ (and no further test is necessary). If you test positive in the first test and negative in the second test, you almost certainly are not HIV+. Conversely, if you test positive in both the first and second tests, you almost certainly ARE HIV+.

This is all extremely logical LJ. And the simple fact is that if the only difference between the Luminol test and the TMB test is that Luminol is more sensitive no one would EVER perform the TMB test. NEVER, EVER, EVER.

I mean seriously Machiavelli. Why would you? Please address this.

There is a reason that forensic manual after forensic manual instruct crime scene police to perform these two tests together and then conduct a third test if the first two are positive.

What is clear is that both are sensitive to different components of blood. Together they narrow the probability substantially that something is blood than the other multiple array of other substances.

To argue that it is blood with a negative TMB test is just downright deceitful.

If Stefanoni, felt that the negative TMB test was providing a a false negative, it would be incumbent on her to take that next step and perform a decisive confirmatory test so the world would definitively know.

In fact it was incumbent on her to do that any way.

 

[yimyammer]

Extraordinary as it may seem, Massei actually ruled the following as evidence of a clean-up in the hallway: 1) there was a bloody partial footprint on the bathroom mat; 2) this print "must have" been made by stepping in the pooled blood in Meredith's room; 3) therefore, there should have been other bloody footprints in between Meredith's room and the bathroom mat; there were no such bloody footprints present; ergo, somebody cleaned up these intermediate bloody footprints in the hallway and the entrance of the small bathroom.

Yet they leave the bloody bath matt in the bathroom as part of the clean up process, come on!

 

[LondonJohn]

Yet they leave the bloody bath matt in the bathroom as part of the clean up process, come on!

Oh yes - I know! We're supposed to believe that Knox and Sollecito were conducting some sort of concerted, selective clean-up. And if that's the case, then if Sollecito had been walking or stepping barefoot in the small bathroom after the murder (as per the prosecution case), it's inconceivable that they would not have looked carefully at that small bathroom during their "clean up".

And if they looked carefully at the small bathroom, we're supposed to believe that they looked at the dilute foot print on the bath mat and thought along the lines of "Oh, look, there's what under closer examination is a dilute blood/water partial footprint. Hmmmm, we can leave that - it's probably too indistinct to be linked to Sollecito. So rather than either washing or removing/disposing of the potentially-incriminating bath mat, let's have a little fun and leave it right where it is!"

It's ludicrous on a number of different levels. And, as you say, the biggest irony and paradox is that the very presence of the bathmat containing blood/water partial print tends in fact to point to one of two (or both) conclusions: 1) there was no clean-up by Knox/Sollecito of evidence of their involvement in the murder; 2) the print was not made by Sollecito. As it happens, the totality of the evidence supports both conclusions.

 

[Chris_Halkides]

sensitivity versus limit of detection

LondonJohn,

I partially agree with you in that we have been using the word "sensitivity" when we should be using the phrase "limit of detection." For the sake of simplicity suppose that we are trying to quantitate a chemical and that there is a linear calibration curve. And suppose that we can run blanks and samples a number of times to obtain an idea of the precision. The discussion below is patterned after Skoog et al., Principles of Instrumental Analysis, 6th ed.

The sensitivity of a machine or method is a "measure of its ability to discriminate between small differences in analyte concentration. Two factors limit sensitivity: the slope of the calibration curve and the reproducibility or precision of the measuring device." In some definitions of sensitivity the latter effect is ignored and then sensitivity is just taken to be slope of the calibration curve.

The minimum distinguishable signal S_m = S_blank + 3•(s_blank), where s_blank is the standard deviation of the blank. 3 is chosen by convention. The limit of detection c_m = (S_m - S_m)/(slope of the calibration curve). Therefore, the limit of detection and the sensitivity are related quantities, in that both include the value of the slope of the calibration curve. However, they are not the same thing, and we are interested in the minimum concentration of blood that can be reliably detected.

 

[LondonJohn]

This is all extremely logical LJ. And the simple fact is that if the only difference between the Luminol test and the TMB test is that Luminol is more sensitive no one would EVER perform the TMB test. NEVER, EVER, EVER.

I mean seriously Machiavelli. Why would you? Please address this.

There is a reason that forensic manual after forensic manual instruct crime scene police to perform these two tests together and then conduct a third test if the first two are positive.

What is clear is that both are sensitive to different components of blood. Together they narrow the probability substantially that something is blood than the other multiple array of other substances.

To argue that it is blood with a negative TMB test is just downright deceitful.

If Stefanoni, felt that the negative TMB test was providing a a false negative, it would be incumbent on her to take that next step and perform a decisive confirmatory test so the world would definitively know.

In fact it was incumbent on her to do that any way.

Yes, the critical thing is the comparison of the sensitivity and specificity of Luminol and TMB.

Luminol does indeed have the highest sensitivity to blood of all the presumptive tests. But it's crucial to understand exactly what this means - and what it does not mean.

Luminol's high sensitivity means that if a substance being tested is actually blood, then it's highly unlikely that a Luminol test will produce a negative result. That's the definition of high sensitivity.

So if a Luminol test comes back negative, you can be virtually certain that what you're testing is not blood.

BUT.... that is very, very different from concluding that if a Luminol test comes back positive, then what you're testing is blood.

And that's because Luminol has very low specificity for blood. In other words, there is a high likelihood of false positives. Therefore, if you have a positive Luminol test, you can't be sure whether or not you have blood.

And that's why any competent and semi-knowledgeable forensic scientist then conducts a TMB test on the sample. Because although TMB has lower sensitivity to blood than Luminol (though it's still a high-sensitivity test), it has far higher specificity. Therefore if a TMB test also comes back positive, you can be far more confident that you're looking at blood.

And here's the most important thing: if a TMB test comes back negative (assuming a prior positive Luminol test), it's in fact far more likely that there's no blood present (i.e. the Luminol positive was a false positive for blood) than that there's blood present (i.e. that the TMB test was a false negative for blood).

In short:

Luminol negative = no blood

Luminol positive = now do TMB test

Luminol positive and TMB negative = no blood

Luminol positive and TMB positive = probable blood: now do confirmatory test.



(A quick scan of some pro-guilt writings - including the ill-informed and subjective "murderofmeredithkercher" wiki-style site - shows that none of the pro-guilt commentators properly understands the position, and that it's highly likely that none of them understands sensitivity and specificity either).

 

[LondonJohn]

LondonJohn,

I partially agree with you in that we have been using the word sensitivity when we should be using the phrase limit of detection. For the sake of simplicity suppose that we are trying to quantitate a chemical and that there is a linear calibration curve. And suppose that we can run blanks and samples a number of times to obtain an idea of the precision. The discussion below is patterned after Skoog et al., Principles of Instrumental Analysis, 6th ed.

The sensitivity of a machine or method is a "measure of its ability to discriminate between small differences in analyte concentration. Two factors limit sensitivity: the slope of the calibration curve and the reproducibility or precision of the measuring device." In some definitions the latter effect is ignored and then sensitivity is just the slope of the calibration curve.

The minimum distinguishable signal S_m equals S_blank plus 3•(s_blank), where s_blank is the standard deviation of the blank. 3 is chosen by convention. The limit of detection c_m = (S_m - S_m)/(slope of the calibration curve). Therefore, the limit of detection and the sensitivity are related quantities, in that both include the value of the slope. However, they are not the same thing.

Absolutely! I was only trying to caution against using the word "sensitivity" loosely, especially when referring to academic material.

Like you, I think that the whole issue around "how little blood (or how dilute the blood) can be present in order for a given test to detect it" should not be dealt with under the explicit term "sensitivity", and that instead the term "phrase limit of detection" or simply "limit of detection" would be far more appropriate (and obviously far less potentially-confusing/misleading).

And I enjoyed your analysis of the measurement of calibration curves - it takes me back to my undergraduate days, where the exact same principles (and maths) were employed in a different context (communications signal detection and validation)

 

[acbytesla]

Yes, the critical thing is the comparison of the sensitivity and specificity of Luminol and TMB.

(A quick scan of some pro-guilt writings - including the ill-informed and subjective "murderofmeredithkercher" wiki-style site - shows that none of the pro-guilt commentators properly understands the position, and that it's highly likely that none of them understands sensitivity and specificity either).

They don't want to understand how it works. It would damage their case against the innocents and let's not let the facts get in the way of their bias.

 

[Machiavelli]

Another lie you are going on repeating. The truth: they (Stefanoni?) were never "caught". The TMB tests were revealed by the prosecution themselves.

When?

Tell me instead, first when you think the the prosecution was “caught”. Because I could recall several moments, but the choice it depends on what moment you ‘chose’ to say that the defence ‘caught’ someone. Chose an event, which you call the ‘defense catching’ someone, and I’ll demonstrate that – whatever event and moment you chose – there was a previous moment when the prosecution revealed the key information first.
In July 2009, for example, Manuela Comodi stated in court that the total amount of DNA on the metal bra clasp was 1.4 nanograms.
Only at that point, the defence complained that they didn’t have that information.
Comodi replied the information was in the SALs and in the quantization data.
Bongiorno requested the data and complained that she didn’t have them. Comodi pointed out that it was her fault if she didn’t have them, and said the prsecution did not object that they have it now (but they should have thought about it before).
So the judge ordered laboratory to give the ‘documentation’. The laboratory turned out the SALs.
Just like this, all the times information release starts from the prosecution. It is never the defence who ‘catches’ anyone.

Even the very existence of the SAL was declared by Comodi first, before anyone ever "caught" her. She was the first one who talked about SALs and laboratory documentation before Massei, not the defence.

Did she say the SAL recorded a negative TMB result? Did she reveal that information while she was contending the luminol hits were made in blood?

Absolutely not. The negative TMB results were just noted in the documentation that the prosecution kindly presented to the defence, despite the defence experts had not attended the meetings they were summoned to with the laboratory staff, and despite the defence did not access the laboratory over the nine months investigation despite defence experts were offered free access to the documentation at Rome laboratory, and they never came.
And, most important, that information was not contending that the luminol prints were made in blood, from the point of view of the prosecution and their experts. It might have been ‘contending’ that only from the point of view of the defence.
It is not an ‘objective’ and ‘manifest’ contention, despite you think it is, for the reasons I already explained.

Had they wanted to hide the SALs, they would have gone on hiding them, destroy them (like the Carabinieri do with their laboratory items) or would have provided a manufactured SAL.

Of course if they did that and it was apparent that the tests had been done from the video as you suggested the last time this came up, they'd have been in a world of trouble.

As I have already said, all information they used to argue about the TMB was extrapolated by documentation which had been previously released by the prosecution
But now you are entangling yourself in your contradictions. If you assert they offered ‘manufactured SALs’, then you should have a shred of evidence of that which you obviously don’t have, and you know that. But now if you instead claim that the defence got the information through the video, then you’re definitely entangled: the defence had been having all those videos for years! The defence experts were even supposed to be present when these videos were shot (they could have actually intervened and could have requested “pleas we want a TMB test on that stain”).
So you are now admitting the prosecution offered all the needed information years before.

Plus of course it's standard practice to verify a luminol hit with a TMB test, not just with ILE but many agencies as well, including the FBI, so it would be expected that those tests were done.

Again, the same contradiction. The Stefanoni’s report contains the templates of all tests doen on samples and items. Now, it happens that not always these templates and pages are correct. There is almost always a TMB test indication, either positive or negative. This indication is missing in the luminol sample templates. If it was so easy to expect this test to be done, why didn’t the defence experts immediately notice that it was missing, and why didn’t they ask about it immediately?
Or maybe they asked, and Stefanoni explained that she did perform the test?

Instead, when requested, they gave information without objecting.

When?

On several dates, several times, depending what information you are talking about.

Perhaps they were foolish enough to think the prosecution would honor discovery and not try to misrepresent the evidence they had, which is what they did when they tried to contend blood for a substance which tested negative for blood without revealing that.

If the defence is foolish, it’s not someone else’s fault. But I seriously doubt the defence was foolish. This defence was rather good and they got all the information they wanted whenever they actually wanted to have it. When they wanted to play games and rise pretexts instead, they did so.

I always remark that you don’t understand the term ‘discovery’ in this system. Discovery means that the defence experts are allowed unfettered access during the investigation, they put their explorer’s helmet on and they to do their research. But they need to actually do their research, they are not supposed to wait for the prosecution to build defence arguments, or to fetch and bring them the material for their research arguments.

The prosecution has a duty to bring defensive arguments when they find elements that they deem they are actual exculpatory evidence, they are not expected to build specious defensive arguments based on irrelevant findings or pretexts.

Moreover in the Italian system the defence not only is not directly provided the documentation (the documentation is only deposited at the chancellery) but in order to have a copy of documentation, they also need to pay to have them (and the payment is not an irrelevant fee: at that time it was something like 70 euros (maybe more) for each support, such as CDs, there was a high fee for paper documents etc.). You may dislike this feature of the system, it’s a legitimate opinion. But it’s an opinion and here we are talking about facts.

There's almost an infinite number of things those luminol hits could be and it is far more probable they are not evidence of someone stepping in with bare feet in diluted blood after a clean up of the murder scene.

No they are not infinite; but I’m not asking for infinite series, I’m asking for one, likely or plausible substance, or in alternative, a substance whose presence has a corroboration.
I am also asking for a dynamic, which must be also likely and probable.

There's little reason to think that they were blood, and if there was blood present (meaning as just part of an overlaying substance on another stain) there's many ways it might have gotten there considering the number of people walking over blood traces and even if they were totally all diluted blood the same dynamic as previously could cause them to be diluted blood made from blood traces getting into moisture being as there's no evidence of a clean up outside crap like this and other indications of a clean-up were it to have happened are missing.

I’m sorry but I think this is a rambling away from logic. Frankly I don’t even understand it. Blood getting into moisture? (what does that mean?) I agree instead with Massei when he says there are obvious indication of a cleanup, even just when you look at at bathmat (completely soakad with water) with 10+ diluted stains on it lying on a clean floor: it means cleanup. Or when you see an isolated footprint in blood whith no trail of prints leading to it, and no source around for it (there is no ‘flat surface’ where someone has stepped, as Hellmann maintains – and if there was, it had been cleaned). This means cleanup. Or even when you notice that one of Rudy’s bloody shoeprints in the trail was missing, it was revealed only by the luminol: how didi t disappear? Or even just when you notice there are three towels soaked with blood: what purpose would you use a towel for, when you have liquids poured around, if not drying up or cleaning up the liquid?

You can't prove they are all footprints, you can't prove who they belonged to if they were, you can't prove they were made at the same time, you got a falsifier that they were blood and even if they were there's nothing about these blood traces outside the bathroom that incriminate anyone specifically of being involved in the murder considering all the people that walked over it after the murder.

I can’t prove? It has already been shown that these prints are compatible with Amanda and Sollecito’s. Do you consider this a probable random event? I can’t prove they were made at the same time? But where’s the logic in this? In order to explain they were made in two or three separate events, I would need two or three scenarios instead than one! It would be a multiplication of improbability, the improbablity of having an isolated print positive to luminol would be multiplicated for all the times this happened. The isolated prints have features that make them very peculiar and improbable, they have a very strong analogy (they have an incredible analogy with the bloody bathmat prints too), a single event, a single explanation for all of them is logically the most probable scenario.

There is no ‘falsifier’, because literature flatly says it’s not true that TMB is a falsifier if the luminol stain is sufficiently diluted.

Finally, it just makes no sense to say the prints are meaningless people walked there after the murder: nobody walked there barefoot, nobody walked there with wet bare feet, nobody walked there hopping or dragging a towel so to produce isolated footprints; maybe you also like to assert that someone stepped with wet feet in Amanda’s room.

 

[Machiavelli]

(...)
Luminol's high sensitivity means that if a substance being tested is actually blood, then it's highly unlikely that a Luminol test will produce a negative result. That's the definition of high sensitivity.

Actually, 'sentitivity' does not tell about probabilities in these terms; it tells about concentrations. If a surface was accurately cleaned, in certain conditions it may be very likely for the Luminol test to be negative or not indicative.

And that's because Luminol has very low specificity for blood. In other words, there is a high likelihood of false positives. Therefore, if you have a positive Luminol test, you can't be sure whether or not you have blood.

TMB has actually a lower specificity compared to luminol.

The advantage of a TMB tst is that it is extremely practical: it is very cheap, easy and quick to perform, and does not strictly require any environmental condition (this is why it is always done).

And that's why any competent and semi-knowledgeable forensic scientist then conducts a TMB test on the sample. Because although TMB has lower sensitivity to blood than Luminol (though it's still a high-sensitivity test), it has far higher specificity.

It's just completely false, as for scientific literature.

Moreover, you also may not know that TMB also would tend react to the same array of substances to which luminol reacts, albeit at different concentrations.

Relatively few substances would react to luminol - and mostly not in a way that would allow them to be confused with blood - there are a couple of recent works by Australian researchers Webb, Creamer, Quickenden about this.

 

[LondonJohn]

Actually, 'sentitivity' does not tell about probabilities in these terms; it tells about concentrations. If a surface was accurately cleaned, in certain conditions it may be very likely for the Luminol test to be negative or not indicative.

You don't know what "sensitivity" means in this context. You're wrong.

TMB has actually a lower specificity compared to luminol.

Oh really? Does it? Cite please...... (I'll give you a hint: you won't be able to produce a cite, because you're wrong).

The advantage of a TMB tst is that it is extremely practical: it is very cheap, easy and quick to perform, and does not strictly require any environmental condition (this is why it is always done).

Yes, I know. Your point is...?

It's just completely false, as for scientific literature.

Cite?

Moreover, you also may not know that TMB also would tend react to the same array of substances to which luminol reacts, albeit at different concentrations.

TMB reacts to fewer non-haematic substances than Luminol, and in ways that are far less likely to give a false positive. You don't know the science, I'm afraid. Please stop pretending that you do.

Relatively few substances would react to luminol - and mostly not in a way that would allow them to be confused with blood - there are a couple of recent works by Australian researchers Webb, Creamer, Quickenden about this.

Simply wrong. Is this due to ignorance, or a conscious attempt to deceive. The biggest single specificity problem with Luminol is that many things make Luminol luminesce at differing levels. It's extremely difficult - if not impossible - to make a quantitative differentiation, since there are so many other huge variables at play (most importantly, the actual amount of Luminol applied, the time since application that the photos were taken, the exposure levels of photos, and the level of background light). As a result, the most that one can usually say is that "it luminesces" or "it definitely doesn't luminesce".


All in all: not good enough, I'm afraid. Have another try.

 

[yimyammer]

Hey Mach,

What's your stance on whether Raf called the police before or after the postal police arrived?

 

[LondonJohn]

Hey Mach,

What's your stance on whether Raf called the police before or after the postal police arrived?

Hehehe.


Hey Mach,

Why is it an internationally-agreed forensic protocol to follow a positive Luminol test with a TMB test, if (as you contend) TMB has both lower sensitivity and lower specificity than Luminol?


*lights blue touchpaper and stands well back*

 

[acbytesla]

Actually, 'sentitivity' does not tell about probabilities in these terms; it tells about concentrations. If a surface was accurately cleaned, in certain conditions it may be very likely for the Luminol test to be negative or not indicative.



TMB has actually a lower specificity compared to luminol.

The advantage of a TMB tst is that it is extremely practical: it is very cheap, easy and quick to perform, and does not strictly require any environmental condition (this is why it is always done).



It's just completely false, as for scientific literature.

Moreover, you also may not know that TMB also would tend react to the same array of substances to which luminol reacts, albeit at different concentrations.

Relatively few substances would react to luminol - and mostly not in a way that would allow them to be confused with blood - there are a couple of recent works by Australian researchers Webb, Creamer, Quickenden about this.

This simply isn't true. False positives in fact ARE COMMON.
There are countless substances that react to Luminol. Luminol reacts to any substance that contains copper, iron, cyanides, bleaches as well as specific proteins.

You need to answer these questions.

1. Why do forensics manuals instruct techs to perform BOTH TESTS?
   [*]Why do forensic manuals instruct techs to perform a confirmatory test?
   [*]Why did Stefanoni perform a TMB test if she plans to ignore a negative result?
   [*]Why can't you see these prints with the naked eye?
   [*]If they were cleaned by Amanda and Raffaele after the crime, why aren't they "streaked"?