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Forensics / DNA

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Forensics / DNA

Post by YNG on 12.01.11 18:06

Forensics / DNA

Part 1 - A critical evaluation ?

According to the Forensic Science Service the question as to whether or not Madeleine contributed to particular samples appears open to interpretation.
The FSS’s report concludes - “ In my opinion, the laboratory results that were attained did not help clarify whether or not the DNA results obtained within the scope of this case were from Madeleine McCann. “

Looking at this statement in terms of forensics the only conclusion anyone could draw from it is that the results proved ‘inconclusive‘, although for some reason the report appears almost to avoid using that term.

There are only ever three types of results in forensic analysis, Conclusive, Exclusion and Inconclusive. Interestingly an inconclusive result indicates that DNA testing could neither include nor exclude an individual as the source of the biological evidence / material.

The reasons why an inconclusive result occurs, for example, is the quality or quantity of the sample may not be sufficient to produce a good result or the sample may contain a mixture of DNA from several people, in other words the sample is contaminated by DNA from someone else or some other object. It’s not unusual to find evidence of additional unreported contributors to evidentiary samples and one of the most common complications in the analysis of DNA evidence is the presence of DNA from multiple sources.

The latter (contamination) appears according to the FSS report to be the reason why they could not clarify whether or not the results of the analysis were from Madeleine. However there are still many outstanding questions regarding the Forensic report that need to answered , some being;

1 - how many times were these samples analysed and are the forensic results we have seen from a first analysis or a further analysis ? -

2 - John Lowe stated in the report that other contributors to one sample could be scientists from the labs. This indicates that contamination of the sample resulted in the laboratory. If this is the case then any extra ‘ components ‘ as he puts it, could not have contaminated the original sample before it got into their hands - So the sample gathered from PDL was not originally contaminated. Also statistical interpretation of results should allow for the possibility that some of the DNA may be due to contamination or other effects caused by working with low level samples.

3 - there is still the outstanding question as to what the blood sample was which was used as a reference sample ( but didn’t come to light until after all the analysis and results were done) .

The Forensic report is dated 6th September.

“ On 12 October 2007, the Forensic Science Service(R) received a blood spot in a cardboard frame (object JRB/1) from Leicestershire Constabulary. That object was inside a sealed package.”

4 - how can John Lowe state this about the sample (286A/2007 CRL 3A) - “if the DNA within the scope of this result originated from more than one person then the result could be explained as being DNA originating from [a mixture of DNA from both] Kate Healy and Gerald McCann”

… and then later state that

“ IF the profiles are equal [match], then that person, together with other persons having the same DNA profile, may be considered as a potential source of the material." – and why state IF the profiles are equal ?

This principal should apply to all samples and therefore does not exclude Madeleine as a potential source of a particular sample / material, on the contrary, it is an inclusion.

5 - why did John Lowe state this “Departing from the principle that all confirmed DNA components within the scope of this result originated from a single source, then these pointed to corresponding components in the profile of Madeleine McCann – however, if the DNA within the scope of this result originated from more than one person then the result could be explained as being DNA originating from [a mixture of DNA from both] Kate Healy and Gerald McCann, for example.”

Departing from the usual principal or procedure is generally only done in special circumstances to make a concession or exception and once again why say - “ IF the DNA with the scope of this result originated from more than one person “ ?

6 - why were the results not given in terms of probabilities ? – “ when a person is not excluded as being the source of an evidentiary DNA profile , the strength of the evidence should be given in terms of probabilities.”

7 - The analysis of the pillow case sample did not determine it definitely came from M., but did confirm it came from a child of the McCann’s , though the twins were ruled out as a possible contributors to this sample as their DNA was obtainable, unlike Madeleine where they had no child or body or DNA to compare this sample to.

It wasn't until after the analysis and conclusions of the report were done that they obtained the blood sample.

I believe that it is important to understand what that means in terms of the analysis and the actual conclusions.

Clearly they found common / familial markers / components in the pillow case sample otherwise they would not have concluded it came from a child of the McCann’s.

But without another reference sample belonging to Madeleine to compare the pillow case sample to, any results could never be conclusive because all they could compare anything to with any certainty were familial components that are common to the parents and siblings.

And it appears that this is exactly what is reflected in the report.

Personally I believe the FSS drew the only possible conclusions they could based on the pillow case reference sample – inconclusive , because they had nothing else other than elimination samples from Madeleine’s parents & siblings to base those conclusions on.

All the pillow case sample provided was a reference sample that showed common markers / components. The reason for this was again because they did not have any other definite DNA sample belonging to Madeleine that we are aware of to compare the pillow case sample to when they were doing the analysis and writing the conclusions, which it appears is exactly what the conclusion of the FSS report reflects – an inconclusive result , because the DNA in the reference sample could have come from anyone closely related and as for any extra components, possible contamination as previously stated, or possibly something else ?

Interestingly people who have Cats Eye Syndrome ( a coloboma of the iris ) have this condition because of the presence of extra chromosomes . It is known as a rare chromosomal disorder.


In his report Mr Lowe wrote: - "Let's look at the question that is being asked: 'Is there DNA from Madeleine on the swab?'

"It would be very simple to say 'yes', simply because of the number of components within the result that are also in her reference sample."


"What we need to consider, as scientists, is whether the match is genuine – because Madeleine has deposited DNA as a result of being in the car, or whether Madeleine merely appears to match the result by chance."
"The expert said the components of the missing girl's DNA profile were not unique to her - in fact some were present among FSS scientists, including himself."


I’m sure most people including myself are puzzled by this statement. How did Mr. Lowe determine that a number of components within this result were definitely identified as belonging to Madeleine McCann, yet then state they were not unique to her and were common enough to belong to FSS scientists including himself ?

In any DNA sample there will always be predictable biological inheritance patterns which identify relatedness ( common markers ) between parents and children / siblings / close family and also common markers which we all share.

However, in order to state that there were enough components for someone to identify an individual, those components had to match that particular individuals reference sample.

"It would be very simple to say 'yes', simply because of the number of components within the result that are also in her reference sample.”


The FSS uses 10 markers to match DNA samples. Using this system the chance of a random match (more than one profile matching a sample from a crime scene) is less than one in a billion.

Dr Peter Gill of the FSS said: “The chance of a random match between 2 unrelated people is on average 1 in 10,000,000,000,000. To be conservative a standard 1 in 1 billion is reported to courts, but in reality the system is much more powerful than this.”



Further media reports ;

“ According to the Portuguese, the British Forensic Science Service told them that DNA evidence found in the couple’s hire car a month after the girl went missing was categorically Madeleine’s.
This led to the McCanns being questioned and made suspects. But one month later the forensic service said it could not be sure whether the DNA belonged to Madeleine, her mother or to her sister Amelie, the report says.”




“ : Found 15 of the 19 genetic markers;
A magistrate and two policemen, including Stuart Prior, responsible for liaison with PJ, were yesterday at the Court of Portimão to try to convince Magellan Meneses, prosecutor, not to release the secret of justice of the whole process of disappearance of Madeleine. One of the things that the British claim that it is not known is the report of the laboratory in Birmingham, which states that “15 of the 19 genetic markers found traces collected in a bag in the car the couple coincide [with the child disappeared].”




There is one outstanding question regarding the Forensic report, which I think everyone should give some consideration to ~ Was the objectives of the Forensic Science Service to find evidence of a missing person in order to strengthen and support other evidence to provide an important link between victim and /or a crime scene, or was it done simply to eliminate individuals from the police enquiry ?



Finally , a little food for thought ~ There is no genetic evidence to prove the profile compiled from both the ‘ blood sample ‘ & pillowcase sample was compatible to any DNA from the child in PDL. There is only the word of parents and friends that it was the same child… and no science laboratory in the world could prove otherwise without a definite DNA sample from the child who was in PDL.

YNG

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Re: Forensics / DNA

Post by YNG on 08.02.11 20:04

Another two important factors


1. According to the FSS a database of DNA profiles from all scientific staff is used to screen results before they are searched.

-This information is relevant in relation to the report which specifically indicates that contributors of one sample could be scientists, rather than clarifying that the analysis of the sample was found to contain only common components / markers.

"The expert said the components of the missing girl's DNA profile were not unique to her - in fact some were present among FSS scientists, including himself."

2. Also according to the FSS when using LCN as a means of testing samples each sample is divided into three parts and two of these are tested. The third is retained for further testing in the event of a failure or to confirm the presence of a mixture.

-Does this then pose the question as to whether or not there is another one or possibly two sets of results and if that is the case which set of results have been released ?


Two Media Reports

“British police officers were yesterday accused of trying to stop DNA information allegedly linked to Kate and Gerry McCann's hire car from being made public.”

“A magistrate and two policemen, including Stuart Prior, responsible for liaison with PJ, were yesterday at the Court of Portimão to try to convince Magellan Meneses, prosecutor, not to release the secret of justice of the whole process of disappearance of Madeleine. One of the things that the British claim that it is not known is the report of the laboratory in Birmingham, which states that “15 of the 19 genetic markers found traces collected in a bag in the car the couple coincide [with the child disappeared].”

____________________
KM : "They want me to lie - I'm being framed. Police don't want a murder in Portugal”

YNG

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Re: Forensics / DNA

Post by YNG on 09.02.11 12:23

Assessing the value of the DNA evidence


In most cases LCN DNA analysis is likely to produce partial or mixture results and any DNA profile will contain components that are not unique to that individual, which applies to any sample. Any conclusion based on this principal can neither include nor exclude a person as being a contributor to a particular sample.

When a person is not excluded as being the source of an evidentiary DNA profile, the strength of the evidence should be given in terms of probabilities.

In this case the probability being, obtaining a match between the suspect / victims profile sample and the evidentiary profile sample - if the suspect / victim is neither included nor excluded as being the source of the evidentiary profile sample.

All that could possibly be established is that there is a certain probability that the evidentiary profile sample either came from the suspect / victim or didn’t come from the suspect / victim or whether or not they may or may not have definitely contributed to it.

Or to put it a different way, a stain may produce an evidentiary profile which may match the profile of the suspect / victim, but this is not necessarily proof the stain itself came from the suspect / victim.
All that can be said is that there is a certain probability that it did.



cont.

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KM : "They want me to lie - I'm being framed. Police don't want a murder in Portugal”

YNG

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