Friday, October 10, 2014

Coincidences? You decide.

I really should get back to the McCann case evidence. Still much to say about DNA, Dogs, slamming doors & whooshing curtains etc Yet I feel compelled to comment on recent events once again.

The Dossier

Many people who have an interest in the McCann case knew that tweets, posts & personal information about anonymous posters on facebook & twitter was being collected in a systematic an organised way. The people doing the collecting & collating made no secret of what they were doing. There was also little doubt that at some point at least some of the information gathered, along with tweets & FB posts deemed to be "hateful" or "threatening" would end up in the hands of the police. Though many seemed to think it would only be used to name and shame on FB or Twitter as had been done by both sides many times before.

The Book by Summers and Swan

This book came as much more of a surprise at least to me. Books of this sort often do come as something of a surprise so there is nothing very unusual about that. The authors did make some effort earlier in the year to contact a few so called "anti" McCann who post on forums, FB & twitter for comment. I have little idea what was said to these people, but it is clear that they did not widely publicise the fact that they had been contacted or that there was a book being written. Thus the book came to most peoples attention towards that end of August only when the pre-publication promotion began. There were notable exceptions to this surprised reaction to the books publication. Some, perhaps most, of the pro McCann lobby seemed to be expecting the announcement and showed little or no surprise. They also seemed to have a good idea that the book would be supportive of the McCann's abduction story.

It seems obvious to me now that the books main aims were twofold:

1. To promote the idea that there was real evidence that an abductor, or at least several people who could have been abductors, were at large in Praia da Luz in spring 2007. While at the same time dismissing, out of hand & with hardly any valid argument or discussion, all evidence that might incriminate the McCanns.

2. To make the readers aware of the online activity by people who question the abduction theory and think that the McCanns were involved in some way in their daughters disappearance. Such people were labelled as "haters"and many details given, often about the worst among them, in an effort to discredit all who post or tweet.

Of these it is possible that the main objective was the second. All the other information about the case was already in the public domain. There was very little if anything new in terms of facts, and certainly no new ideas or leads. However the so called "hate campaign", which is not a campaign at all, has not been widely reported. Only a few isolated incidents such as the silly London marathon "anyone got a gun?" post on facebook have been reported. It seems quite possible that the book was written, at least in part, with the intention of spreading the message that the McCanns were the subject of a "hate campaign" to as wide an audience as possible. Of course the seemingly very low book sales mean this objective wasn't achieved.

We now know, through a freedom of information request, that the authors tried to coordinate the publication of the book with the end of the Operation Grange investigation. The police refused a request for information about the end of Operation Grange

The Times lawsuit.

This was announced at the beginning of August 2014. The offending article had appeared in October 2013 soon after the CrimeWatch program. The Times had published an apology/correction soon after the original article was published. I don't know exactly when the lawsuit was filed, but it appears to have been in July or August with the resulting out of court settlement being made soon after the Summers and Swan book was published. 

The Damages Trial 

The trial in Portugal in which the McCanns are seeking damages from Goncalo Amaral and others had been hearing evidence in June and was due to conclude with the Judges verdict in September.


Are these coincidences?

The book publication, lawsuit settlement and dossier all occur within a few weeks of each other.

The book publication, lawsuit and dossier all occur soon after Operation Grange completes digs and interviews in Portugal.

The book, lawsuit and dossier all occur at the same time as the judge in the damages trial was due to give a verdict.

Which of the explanations below seems more likely?

1. It is possible that the book publisher thought Sept 11th was a good time to release the book entirely independently & without knowledge of the dossier or the lawsuit. Perhaps thinking that the trial verdict would be at that time and chose not to postpone when it became known the trial verdict would be delayed. 

2. It is possible that the McCanns & their lawyers decided to sue The Times entirely independently & without having any influence over the book publication date or the dossier release. The long delay between the offending article and the lawsuit being due to?......I'm sure there must be a reason,but I can't think of one.

3. It is possible that those who compiled the dossier handed it to..... well we aren't sure who they handed it to, but never mind.....without having any influence over the book publication date or the timing of the lawsuit settlement. Presumably the dossier just happened to be completed at the beginning of September.

4. It is possible that the McCanns or people acting on their behalf could have exercised control over the timing of all three of these events in an effort to get maximum impact at the same time that a verdict was due in the damages trial in Portugal. 


While I was writing the above Sir Bernard Hogan-Howe spoke in an interview and said that the  the dossier was handed to the police by the McCanns. He may have made a mistake about this, but if he is correct it supports the suggestion that the McCanns might have coordinated these events.

Monday, October 6, 2014

That Dossier

Now that I have had a little time to reflect on the shocking news about Brenda Leyland that I first heard late last night & read and listen to some of the reports, comments & spin today I have collected my thoughts. Here they are:

1. No one is in a position to say whether Brenda's tweets were illegal as this has not been tested in court.

2. Everyone has the right to express their opinion as long as doing so falls within the law.

3. The dossier was compiled by persons who wish to remain anonymous to the wider world. They had every right to compile their dossier & if they believed they had unearthed illegal activity to pass it on to the police.

4. They also had the right to pass their dossier to  and to those who run social media platforms such as twitter and facebook if they believed they had uncovered contraventions of the terms & conditions of those platforms.

4. The dossier compilers DID NOT have the right to give, or worse still sell (I do not know whether it was sold I am simply saying that it would be even worse if it had been sold), the dossier to any media outlet.

5. Any media outlet receiving such a dossier DID NOT have the right to publish the name or any other personal details of anyone named in the dossier.

6. The media did have the right to run a story describing in general terms what was in the dossier and to say that it was in the hands of the police & CPS who were considering whether any laws had been broken and whether anyone should be charged.

7. By publishing the name & image of someone named in the dossier and by calling them a troll & member of a hate campaign the media in general, & SkyNews in particular, contributed enormously to the circumstances that caused Brenda Leyland to kill herself.

8. I am now surprised that I find myself in partial agreement with the "Hacked Off" campaign and G McCann. The media in the UK need to be subject to greater control. Though I disagree about how such control should be achieved.

9.  I expect "Hacked Off" & G McCann to publicly condemn the actions of the media with respect to Brenda Leyland in particular and the dossier in general. If they do not they will be revealed as the hypocrites that some people think they are.

10. The people who compiled the dossier should publish, anonymously if they wish, details of exactly to whom they gave the dossier, when this was done and whether any money changed hands. Once again failure to do so will reveal them to be hypocrites.

Sunday, October 5, 2014

RIP Brenda Leyland

RIP Brenda Leyland aka @sweepyface. My thoughts are with your family & friends.

I don't agree with some of the things you posted & tweeted, but I have seen nothing you posted or tweeted that merited the treatment you received at the hands of the media and the real internet trolls, harassers & stalkers.

I hope that in time some good will come from your untimely death,

A message to all who post opinion on the internet.

PLEASE PLEASE, think about the possible consequences of your posts before you publish them.

Friday, October 3, 2014


Before I return to analysis of evidence in McCann case I thought I would write a short post inspired by the recent internet troll saga in the McCann case.


First let me make my position crystal clear:

No one should feel it is their right to ridicule, insult, harass or make untrue or unprovable accusations about anyone, either on the internet, in newspapers on TV/radio or anywhere else. Freedom of speech is a right that carries with it responsibilities. No one should abuse this right.

There is absolutely no doubt that, for want of a better phrase, "internet trolls" comment on the McCann case. These people "infect" social media & the internet in general with inappropriate and occasionally highly offensive material. Trolls on both sides of the debate engage in these tactics. Anyone reading #mccann on twitter can quickly see the daily attempts by trolls on both sides to provoke, insult and attack the other.

Trolls who claim to support the McCann's clearly attempt to provoke more and more outrageous comments from their opponents. Once they succeed they then re-post these comments in a forlorn attempt to claim the moral high ground. These McCann supporting trolls also cherry pick items from the evidence and claim it "proves" their point while at the same time ignoring evidence that suggests the opposite. They insult anyone who questions their opinion, sometimes disgracefully invoking mental health issues. They present strawman arguments (effectively lying) in an effort to discredit their opponents position. They are rude, intolerant, aggressive and spiteful. Most claim to do this to support the McCann family, but how can their actions do anything of the sort? Pouring petrol on a fire doesn't put it out. If the McCann's are aware of their actions, it is hard to imagine they are not, they must surely be appalled by what they see.

Trolls, some of whom claim to support Madeleine, by claim that the evidence proves her parents are guilty of some crime (anything from negligence to murder) are equally shameful. For example there are large numbers of photoshopped images circulating. Some are obviously photoshopped and meant in jest (albeit often in very poor taste), but others are circulated as if they are genuine and can create an entirely false impression. Cherry picked items of evidence, often inaccurately quoted, are posted along with claims that this proves the McCann's guilt. Suggestions that there may be innocent explanations for these are ignored or ridiculed. They frequently accuse the McCann parents of various criminal acts, none of which can be proved & occasionally one will make an outrageous threat to harm the McCann family in some way. To claim that these actions are in any way supporting a missing child is ridiculous and offensive.

Facebook groups, Blogs and forums are similarly infected by these trolls. In my opinion none of the trolls has a genuine interest in any of the following:

1. Finding out what happened to Madeleine McCann.
2. Supporting the McCann family over the loss of their daughter.
3. Finding Madeleine.

So I make this appeal to the trolls on both sides. STOP! If you write a tweet or post which only has as it's only purpose insulting, provoking or accusing someone else don't post it.

If you want to why not START, engaging in a proper discussion and analysis of the evidence. Accept your own shortcomings & the shortcomings of others and try to improve the overall level of understanding about this case and perhaps others. DON'T be taken in by propaganda from either side. READ the PJfiles & RESEARCH other relevant information, such as interviews, press articles and background information using all means available to you.
Above all KEEP AN OPEN MIND & be receptive to different opinions and ideas.

Finally, NEVER forget that at the heart of this case is a missing girl who was almost 4 years old when she vanished & would be 11 now. She is more important than your petty point scoring and childish insults and games. Her disappearance remains an as yet unsolved mystery. At the time of publishing this blog anyone who claims different is a liar.


Not everyone who comments on the McCann case online is a troll. There are people, who do seem to have a genuine interest in The McCann case. They fall into several categories

1. Those with a genuine interest in finding out what happened to Madeleine.

Some think the balance of evidence supports the abduction hypothesis, some think that it supports anything but the abduction hypothesis, some are genuinely undecided, but all seem to share a genuine interest in the mystery and choose to spend their leisure time discussing the evidence and various hypotheses to explain Madeleine's disappearance.

2. Those who campaign for missing people & children.

Usually these people believe that Madeleine was abducted, or take the view that it is better to believe this unless it is proven otherwise.

3. Those who are concerned about paedophilia and government cover-ups in the UK & who think the McCann case is an example of one or both.

Often referred to as "conspiraloons" such people are very important in a democracy. Usually they are completely mis-guided, but every now and again they shed light on something that really needs to be uncovered. Unfortunately they can be over zealous in their words and actions which gives more fuel for the McCann supporter trolls to throw on the flames.

4. Those with a casual interest in the case.

Thursday, October 2, 2014

All is clear now. So I'm back.

So now I know what the advice was all about.

I don't think my blog contained any threats or abuse aimed at Kate & Gerry McCann. Quite the opposite in fact. I have pointed out ways in which the existing evidence might be used to help clear them of any suspicion.

Today's papers and SkyNews broadcasts make it clear that such suspicion does exist. It exists for one very simple reason. The case of the disappearance of Madeleine McCann remains a mystery. No one can even state with 100% confidence what crime occurred. In fact it is still not 100% clear when the crime occurred. So, I have decided to re-open my blog.

The detailed S&S book review may have to go on hold. Others have done a better job of reviewing the book than I was doing anyway. I have finished reading the book now and almost wish I hadn't bothered. It really isn't a very good book. My criticisms of the early chapters apply equally to the later ones. I was hoping to find some revelatory section that would prove to me that Madeleine was abducted. There was no such section. If there is demand I may return to the detailed review.

I remain mystified. The evidence in the public domain casts some doubt on the McCann version of events, but does not disprove those accounts. I will continue to post about aspects of the case that I think are important because they are open to further investigation & hopefully progress.

Tuesday, September 30, 2014


To clarify. I have been advised & persuaded that a blog under my real name is not advisable.

Friday, September 12, 2014

The hire car sampling.

This will be a shorter post and I hope quite easy to follow.

In the last post I showed how the existing DNA profile from the car sample could be used along with DNA profiles from McCann family & friends + a others to enhance our understanding of who might have contributed to the DNA profile and thus how likely it is that Maddy was one of those people.

Now I would like to consider what else should have been done in 2007 as soon as the DNA profile was known.

The whole of the carpet from the car boot should have been retained and sealed as evidence. It should have been cut into many (at least 100) small pieces in a grid like fashion ad each piece subjected to DNA extraction and LCN DNA analysis.

In addition random samples should have been taken from all interior areas of the car, seats, carpets, swabs from door handles, windows, floor (e.g.under car boot carpet) etc. Perhaps a further 100 samples. These should also have been subjected to LCN DNA analysis.

What would this sampling & testing reveal?

Had this been done several things might have been revealed including:-

1. Was it possible to get DNA profiles from any other parts of the vehicle?

2. Were the 15 (or more or less) Maddy markers present anywhere else in the vehicle?

3. Were there parts of the vehicle that gave single person DNA profiles? (I am aware of the Gerry McCann profile from the key fob I'm talking about the car itself.

4. Were the 15 Maddy markers present in other pieces of carpet from the boot? 

5. Were the 22 other markers from the car boot present in any other samples?

6. Were there samples that included markers not found among the 37 in the car boot sample?

7. Was there an area of the car boot carpet that gave significantly poor or zero DNA results?

What might any or these results indicate or prove?

1. If yes then these profiles might be used to show how the 15 Maddy markers could have come together in the single sample from the boot. 
2. If yes then the pattern of profiles seen would show whether the 15 Maddy markers were present in only one or a few areas of the car or were widespread. If they were present only in one area that would indicate her body could have been placed in the boot at some point. If widespread the chances are that these markers are coming from the DNA of others.

3. Any single person profiles would identify people who had definitely been in the vehicle (or their DNA transferred there. Clearly a single person profile that matched Maddy's would be significant, but others could also be used in a subtraction analysis on other samples.

4. If yes this would identify an area (or areas) that had Maddy's markers. The size and shape of any such areas would be very informative. e.g. a few drips spread out, a single small area consistent with a pool of liquid soaking into the carpet, a ring with a blank area in the center consistent with cleaning of a spill or leak etc

5. The presence of these other 22 markers in other samples, especially any single ID samples would permit subtraction analysis on the boot sample

6. This would show whether the car boot sample contained all the markers present in the car or not. Creating a complete picture of the amount of DNA contamination in the car.

7. This would indicate an area that had been specifically cleaned shortly before the car was seized as evidence.

Why weren't these things done?

I am at a complete loss to explain why these things or at least some of them were not done. The case was huge worldwide news at the time. The McCann's were being suspected of disposing of Maddy's body. The evidence from the single sample in the car boot suggested that could be the case but was inconclusive. Here was a great opportunity to either clear the McCann's or gather evidence that would help to prove they did dispose of Maddy's body. Why did no one.... NOT EVEN THE McCANN's themselves..... insist that this car was examined thoroughly and every scrap of evidence extracted?

Was Maddy's DNA in the hire car?

So we come to the all important question:- Was Maddy's DNA in the hire car?
Perhaps we need to phrase this question a little better before we move on. I prefer:- Was DNA from Maddy present in the sample taken from the boot of the McCann's hire car?

This question has already been answered in the FSS report >John Lowe said the answer was "I don't know."  (I've put that in "" for effect I'm not saying those were his precise words) It is an accurate answer as far as it goes, but as I will show here John Lowe could have said more, MUCH MORE.

Who's DNA could have been in the sample? 

(To be clear, in this post "the sample" always refers to the sample collected from the boot of the hire car)


How many people? 3, 5 or more?

In my previous blog I explained that the sample contained DNA from several people. Lowe says at least three and possibly as many as five. He does not say how he arrives at this conclusion, but I can make a reasonable guess. The "at least three people" almost certainly comes from the observation that some loci contained five (or possibly six) different markers. The only way 5 markers can be found at one locus is if at least three peoples DNA is in the sample.This is because each individual person can contribute a maximum of two markers and minimum of one marker to each locus. Hence 5 markers requires at least three people (2 contributing 2 markers and 1 contributing 1 marker).
It appears that Lowe may have gone on to assume that because he never saw more than 5 markers at a single locus a maximum of 5 people's DNA was present (i.e. if each contributed 1 marker). This is possibly true, in a practical sense, as it is extremely unlikely that DNA from more than 5 people would produce a profile with a maximum of 5 markers at any locus, but in fact it is theoretically possible for the maximum number to be more than 5.

One question we might hope to answer is whether the number of people contributing to the profile was 3, 4, 5 or more than 5. Assuming that the most markers seen at any single locus was 5 I calculate that it is most likely that only three people contributed to the sample, but cannot rule out the possibility that it was more than three. The maths is complicated by several factors. 1. Each marker occurs at a different frequency within the population. 2. We don't know whether the contributors were related or how closely they were related. 3. We don't know how many loci had 5 markers present in the sample. Hence it is not possible to say any more than it was probably three people, but could have been more than three.

Which people have DNA in that sample?

It would be easy to say that the DNA could have belonged to anyone. This is simply not true. The DNA can only have come from a limited number of people who had been in contact with the car or the sample after it was collected from the car. It would have helped greatly if several samples had been taken from different parts of the vehicle & all subjected to LCN analysis. The fact that this was not done is a great pity as it might have allowed a simple subtraction analysis to have been performed. Here is how it works:-

The group would include people at the car hire company, McCann's (including Maddy) + friends & family and forensic scientists + others who had hired the car.

Anyone whose profile has a marker from the 8 loci that is NOT present in the sample can be eliminated. This would probably take care of most people. All of the people remaining would be potential donors to the sample. A potential breakthrough for the case could be made at this point. If it turns out that Kate & Gerry McCann are both potential donors to the sample it becomes highly probable that Maddy's DNA is not present. Their combined DNA would account for all the 15 markers from Maddy's profile. It would not rule out completely that Maddy's DNA was also present, but the odds on this being the case would fall dramatically. Furthermore if it was shown that Kate and Gerry McCann could NOT be contributors to the sample it would greatly increase the chance that Maddy's is in the sample along with all that that implies.

The group of people who are potential contributors could then be further analysed in a group inclusion analysis. Here is how it works:-

All possible combinations of three people are generated. This might be quite a large number of groups, but still possible to do by hand and easier with a computer. All combinations that do not recreate the exact profile seen can be rejected. Most combinations should be rejected by this process that is just a statistical fact. The FSS report is somewhat disingenuous about this when it says that many people are potential contributors to the sample including the report writer Lowe himself. This may be true, but what he does not say is that only a very few combinations of three people who had access to that vehicle or the sample would generate the EXACT profile that was obtained. 

Without access to the full profile obtained from the sample and the DNA profiles of people who are potential contributors to the sample (i.e. those who had access and who's DNA profile fits with the 37 observed markers) it is impossible to know how many groups of three people would be found. It is likely to be a very small number, possibly even zero and almost certainly no more than 5.

If there are no groups that can account for the sample profile it suggests that at least one individual is missing from the analysis or that the sample contained DNA from more than 3 people. The analysis can now be repeated looking at groups of 4 & 5 in fact this should be done regardless of the findings for groups of three.

If there are groups that can account for the sample profile their composition should be studied. There are three possibilities.

1. All the groups contain Maddy.
One key question is do all the groups that account for the sample profile contain Maddy? If the answer is yes then we have once again greatly increased the odds that Maddy's DNA IS present in that sample. Of course this is still some way short of proof, but it would be an indication that the parents should be considered suspects and the possibility that Maddy's body was moved using the hire car.

2. Some groups contain Maddy and some do not.
If there are groups of three people that can product the complete profile of 37 that do not contain Maddy as well as groups that do contain Maddy it would not rule out the possibility that Maddy's DNA was present in the sample, but it would provide a clear and obvious explanation for the presence of the 15 markers without Maddy's body ever having to be in the car thereby shifting suspicion away from the parents.

3. None of the groups contain Maddy.
The final possibility is that only groups not containing Maddy can account for the sample. This is highly unlikely, but if it were to happen it would strongly suggest that Maddy's DNA was not present in the sample.

As I said earlier the group inclusion analysis should be repeated for groups of 4 & 5 people in order to get a clear picture of which groups of people could have produced the observed profile. The composition and number of these groups should then be studied. For example if the only group that can account for the profile is Maddy + a Portuguese  forensic scientist + an FSS forensic scientist this would almost constitute proof that Maddy's DNA was present in the hire car. Alternatively if a group comprising Sean + Amelie + John McCann could account for the sample profile this would provide a strong indication that the sample from the car boot did not contain Maddy's DNA.

Could Maddy's DNA have been in the car without her body being there?

The simple answer to this question is "yes". It is theoretically possible that her DNA might have been transferred from luggage or clothing that she had used or worn to the car boot. However this is rather unlikely. It is also important to note that the DNA sample was obtained from the spot in the car boot to which the CSI dog alerted. So while DNA transfer cannot be ruled out it can be considered unlikely.


1. Analysis of individual DNA profiles and the profile of 37 markers found in the sample can ELIMINATE a large proportion of possible donors and IDENTIFY a smaller group as genuinely potential donors to the sample.

2. If Kate & Gerry McCann are eliminated as potential donors to the sample it greatly increases the probability that Maddy's DNA is present in the sample.

3. If Kate & Gerry McCann are identified as genuinely potential donors to the sample it greatly reduces the probability that Maddy's DNA is in the sample.

4. It should be possible to identify at least one group of 3,4or5 people whose DNA could have been on the car boot sample whose combined DNA profiles match exactly the profile obtained from the sample. The composition of this group or groups might greatly increase or decrease the probability that Maddy's DNA is present in the sample.

5. Most important is the fact that this type of analysis and conclusions is still possible today. The full 37 marker DNA profile from the sample should be available (if it has been destroyed someones head should roll). DNA samples could be obtained from all people who used that car while in the McCann's possession and earlier. Forensic scientist/tech DNA profiles should be on file. 


We are not quite finished with the car yet. My next post will consider what else could have been done in 2007 to confirm or not the presence of Maddy's DNA in the car.

15/19 or 15/37 & 100% or NOT 100%

There are people in the world who are convinced that Madeleine McCann was not abducted. They believe that Kate & Gerry McCann hid Madeleine's body following her death. One central plank of evidence in this hypothesis is the DNA that was found in the boot of the car hired by the McCann's about three weeks after Madeleine was reported missing. They argue that the only way her DNA could have been in the car is if they moved her body at some time after they hired the car.

There has been considerable debate about whether the DNA profile obtained contained Madeleine's DNA or not. The report by the now disbanded FSS (Forensic Science Service) says clearly that it is impossible to say for certain. Unfortunately it does not go on to say anything else about this sample. There is no attempt to say how likely it is that the DNA came from Madeleine or not. So we are left not knowing whether the chance it is Madeliene's DNA is 1%, 50%, or 99%. All we know is that according to John Lowe of the now defunked FSS that it is not 100%.

Perhaps that would be the end of the matter, but people have taken sides on this issue. Some say it was her DNA some say it wasn't. Both points of view are wrong because no one can say for certain either way. However it is possible to gain some understanding how likely it is that this sample does contain DNA from Madeleine McCann. This blog will attempt to do that over the next few weeks.

First of all some background about DNA identification.

The FSS test involves looking at 10 different loci (locations) in human DNA. Each location (locus) has two copies sometimes called markers or alleles. The two markers at a locus are often different to each other but can be identical. So by looking at 10 loci the FSS identify a maximum of 20 markers.
In Madeleine's case there are actually only 19 markers because at one locus the two markers are identical.

Each individual person has a unique combination of markers and this is called their DNA profile or fingerprint. Some elements of a DNA profile will be shared but the total combination of 20 markers is unique to an individual except in the case of identical twins who will share identical profiles.

You may find it helpful to think of the following analogy. Imagine that each marker is a coloured disc. Now imagine that each locus is a number from 1 to 10 and that one of these numbers is written on each disc. The discs can be any one of many different colours and they can have any number from 1 to 10. Each person gets two discs with the number 1, two discs with the number 2 and so on till they have 20 discs. Can you see how unlikely it is that any two people will get exactly the same set of discs?

In reality everyone gets 10 markers or coloured+numbered discs from their father and 10 from their mother. This means that everyone shares exactly half their DNA profile with their mother and the other half with their father. See the diagram below

The selection of discs from mother and father is completely random. This means that although two children (even twins though not identical twins) have the same parents they have very different DNA profiles. See diagram below:

The one exception is identical twins because they form from a single embryo identical twins will have identical DNA profiles to each other. As far as we know Maddy did not have an identical twin sister so there is no need to worry about this possibility.

15/19 OR 15/37 

Now we know the genetics behind DNA profiles we can push on to the next subject namely was it 15/19 or 15/37?

The answer is BOTH! Here is why.

Maddy has only 19 markers because at one locus she inherited exactly the same marker (numbered+coloured disc) from Kate as she did from Gerry. In the example above this happens at location 6 (child 1).

We have to assume that when the FSS tested the sample only 8 loci gave a positive response. That is to say they were not able to determine the colour of the discs at two loci. This can happen and I may deal with why in a later blog. For now all we need to know is that 8 loci gave a result (colours in our analogy) and 2 loci didn't. One of the eight that did give a result gave only one colour while the other seven gave two colours making a total of 15. This is exactly what you might expect if loci 1 to 8 gave a result and 9 & 10 didn't in the example above.

Great you say, that means 15 markers (out of a total of 19) all matching Maddy's DNA. So it's 15/19! Yes that is true. However the FSS say that they didn't just get one or two colours for each locus, they got more. This can happen if DNA from two or more people gets mixed in the sample. So if we take loci 1 to 8 from the sample above and count the number of markers we get from a mixture of Mum,Dad and Child 1 in the example above we get 31 markers. The exact number of markers obtained will depend on how many people's DNA is mixed and how many markers they share. In the McCann case FSS say they found a total of 37 markers at the 8 loci. It is not possible in a mixed DNA sample to say which marker came from which person unless you already know who the contributors were. So while we can say that 15/19 of Maddy's markers are present in the sample we must also say that 15/37 of the total number of markers in the sample match Maddy's DNA.


Once again the answer is BOTH! (Well sort of) 

We know that only 8 loci gave a result and we know that all 15 of Maddy's markers for those 8 loci were present so it is a 15/15 i.e. 100% match. If only 14 of Maddy's markers for those 8 loci had been present the match would be 14/15 i.e. 93.333% and we would be able to say with a high degree of certainty that Maddy's DNA is NOT present in the sample. 
However because it is a mixed sample it is not possible to say for sure (i.e. 100%) that all the markers that match Maddy's DNA came from the same person. So although the match IS 100% we cannot be certain that the DNA came from Maddy. This seems to be the bit that confuses many people. If you are confused perhaps thinking about the coloured+numbered counters can help. Here is another diagram to help.

This diagram clearly shows that it is theoretically possible for the same 37 marker profile to be produced from Maddie's DNA mixed with two strangers DNA or from Kate's DNA mixed with DNA from two strangers. (These are only representations of what Kate & Maddy's DNA profiles look like as numbered discs, but they provide an accurate illustration of principle).

In my next installment I will consider how likely it is that the 37 markers contain DNA from Maddy.