Luke's DNA

[moggrey1]

Hi, i was wondering if someone could help me. I've been reading up on this case after seeing the documentary and (after being totally convinced Luke was innocent!) i am more of the opinion that he is guilty. The thing i'm looking for some clarification is this if ok: the people in the "Luke is innocent" camp seem to continually argue about the lack of his DNA on the body. However, i have read that there WAS in fact DNA on the body it was just that because they had been in a relationship and therefore highly probable that this would be the case, they agreed to discount it. is this correct, as that seems to be the main thing the innocent group seems to go on about but i thought this had already been disproved?

[mrswah]

Hi, i was wondering if someone could help me. I've been reading up on this case after seeing the documentary and (after being totally convinced Luke was innocent!) i am more of the opinion that he is guilty. The thing i'm looking for some clarification is this if ok: the people in the "Luke is innocent" camp seem to continually argue about the lack of his DNA on the body. However, i have read that there WAS in fact DNA on the body it was just that because they had been in a relationship and therefore highly probable that this would be the case, they agreed to discount it. is this correct, as that seems to be the main thing the innocent group seems to go on about but i thought this had already been disproved?

I read that Luke's DNA on Jodi was discounted, and vice versa (can't recall where I read it), since it would be expected that a couple in a relationship would have each other's DNA on them, and so would prove nothing.

Welcome to the forum!  Please would you introduce yourself in the "New Members" section.

[Rusty]

Hi, i was wondering if someone could help me. I've been reading up on this case after seeing the documentary and (after being totally convinced Luke was innocent!) i am more of the opinion that he is guilty. The thing i'm looking for some clarification is this if ok: the people in the "Luke is innocent" camp seem to continually argue about the lack of his DNA on the body. However, i have read that there WAS in fact DNA on the body it was just that because they had been in a relationship and therefore highly probable that this would be the case, they agreed to discount it. is this correct, as that seems to be the main thing the innocent group seems to go on about but i thought this had already been disproved?

The DNA stuff is irrelevant. Let's say there were full profiles, although there were partial matches. How could the crown use that to convict? When the pair were in an intimate relationship. So his DNA or that of Jodi's in this case wouldn’t prove innocence or guilt. It could have been simply argued, that because they were in a relationship and spent time at school that day.

This ship has sailed a long time ago, pretty sure, and please correct me if I'm wrong, one of the appeals was based on the forensic science. It failed.

We need something new. It is rather tiresome, repeating the same stuff over and over, year after year. When there is a new audience to try sell the story too.

[moggrey1]

I appreciate it's irrelevant, i just wondered why so many people still say there was NO dna found and use it as the basis of their belief that he's innocent. if it were more widely known that there WAS evidence, it was just decided to be discounted due the nature of their relationship, i would have thought that might shut a lot of them up lol.

[Brietta]

I appreciate it's irrelevant, i just wondered why so many people still say there was NO dna found and use it as the basis of their belief that he's innocent. if it were more widely known that there WAS evidence, it was just decided to be discounted due the nature of their relationship, i would have thought that might shut a lot of them up lol.

Anyone with a smidgeon of knowledge about the case knows of the agreement made between the prosecution and the defence.

In my opinion it is a forlorn hope that some individuals will look rationally at facts which is why there is so much internet concentration on misleading out of context comment and innuendo.

[Bullseye]

Hi, i was wondering if someone could help me. I've been reading up on this case after seeing the documentary and (after being totally convinced Luke was innocent!) i am more of the opinion that he is guilty. The thing i'm looking for some clarification is this if ok: the people in the "Luke is innocent" camp seem to continually argue about the lack of his DNA on the body. However, i have read that there WAS in fact DNA on the body it was just that because they had been in a relationship and therefore highly probable that this would be the case, they agreed to discount it. is this correct, as that seems to be the main thing the innocent group seems to go on about but i thought this had already been disproved?

My understanding is there was no full profile of Luke on Jodi or anywhere at the crime scene, there was a full profile found of sk found on Jodi’s T-shirt and/or bra but as he was Jodi’s sisters boyfriend and Jodi was wearing her sister’s t-shirt this was not found to be suspicious. Transfer of dna soaked from the T-shirt to the bra due to rain water I think.
There was partial dna found that matched part of Luke’s profile, but as it’s partial it also matches parts of thousands of other people. So no use, unless they can get to retest it, after 20 years they might be able to get a better profile.
There was dna of Jodi found on a pair of Luke’s trousers found in a bag he used when he stayed at his dads I think, this is the dna they said was not connected to the murder, they were not trousers worn that day and as they were bf and gf, so again nothing suspicious it was agreed.

[Chris_Halkides]

With the indulgence of the moderators, I will repost something I just put on another thread.

"Ms Ure said a stain on a bra Jodi had been wearing showed DNA traces from more than two individuals - some of which matched parts of Luke Mitchell's genetic profile." BBC

I would like to see a table of loci for myself, or still better, the electropherogram. This statement is open to two kinds of interpretations. I will assume no more that two loci for the sake of simplicity, and I will at first treat the DNA as if there were only one contributor, also for the sake of simplicity.

Interpretation 1: They found a locus for which the alleles were the same as Mr. Mitchell's. A single locus is not a full profile; you might narrow down the number of donors to, say, 10% of the population (it depends greatly on the particulars), but that is nowhere near the full discriminatory power of DNA.

Interpretation 2: They found one locus the same as Mr. Mitchell and one locus that was not the same. If that were true then Mr. Mitchell is excluded as a donor.

But the difficulties in the statement above go beyond this first problem.  A three-person mixture is much more difficult to disentangle than a single profile is.  Let me quote from an article at NIST (USA).  "This illustrates an important point about DNA mixtures: Just because a person’s alleles appear in a mixture does not mean that person contributed to it. The alleles may have come from some combination of other people who, between them, have all the allele types in the suspect’s profile." https://www.nist.gov/feature-stories/dna-mixtures-forensic-science-explainer. The kind of software mentioned in this article was not, to the best of my knowledge, available at the time of the murder (it was introduced around 2009).  This type of software has itself generated controversy, although it also has some potential advantages.

For these reasons Ms. Ure's statement is close to meaningless.

The above is something I wrote earlier today.  Let me expand a little.  I went back an old blog entry that concerned the lack of DNA evidence in the Duke lacrosse case of 2006, and I found two quotes that might be helpful.

"For instance, William Thompson of the University of California wrote “It depends on the way the analyst chooses to interpret the mixed profile. In the cases I look at, the analyst are usually quite lenient about what they will call a ‘match.’ A mixture of DNA from three or more men can often be interpreted in a manner that allows a very substantial fraction of the male population to be ‘included’ as a potential contributor.”"

"But William Shields of the State University of New York wrote, “If three, four, or more people donate DNA then there will be so many alleles in a mixture that very few if any people can be excluded as potential contributors. In such an event the evidence does become useless.”"

https://creativedestruction.wordpress.com/2006/04/15/experts-answer-what-does-dna-evidence-prove/

[Venturi Swirl]

Relevant to the Madeleine McCann DNA findings also.

[Chris_Halkides]

I have not been able to obtain information on the putative agreement between the prosecution and defense on how much DNA evidence was excluded from the trial.  Was some or all of it left out?

[Parky41]

I have not been able to obtain information on the putative agreement between the prosecution and defense on how much DNA evidence was excluded from the trial.  Was some or all of it left out?

Obviously all was not excluded - SK's DNA and that of the condom were inclusive? As was the trousers - the agreement was made after the trousers and bra:

I have asked Ms Lean about this agreement on occasion - She has not denied it took place, one can not deny what happened. Very much an evasive response which is often the case. Her response was that of a question "how can there have been an agreement made if SK's DNA was discussed?"

The agreement was around that of DNA being more than probable of belonging to LM. The thing, and pretty much why the agreement was made - an endless debate. Of innocent transfer, that this young couple had been in a relationship.

And that my understanding is that multiple partial profiles were obtained out with that of a full profile? With a significant amount of locus with alleles attributable to LM. Not the amount required, conclusively to say that they were his.

Interpretation 1: They found a locus for which the alleles were the same as Mr. Mitchell's. A single locus is not a full profile; you might narrow down the number of donors to, say, 10% of the population (it depends greatly on the particulars), but that is nowhere near the full discriminatory power of DNA.

As you clearly state of the full discriminatory power of DNA, and of as little as 10% of the population. There were in fact multiple partials with several locus with alleles the same as LM with none different. Thus LM could definitely not be excluded as a contributor. And there were several locus in which the alleles were the same. Different partials, different locus with same alleles the same as LM.

I tried to simplify this in another post - with using using numbers and letters in boxes.

The point being, of that of the law of averages - when one has multiple partial profiles - each an every one having the same alleles at locus of LM.  That he could not be excluded from. That this 10% of the population is reduced significantly. That is more than probable that they did in fact come from the same male.

If I am talking absolute rubbish then I am sure you will tell me?

The agreement - And of what did matter, is anything that could connect LM to the actual murder.  A significant form of DNA that could place him at the murder - finger nails from the victim, skin/hair and the such like.

Anything upon LM himself - of which there was not.

Therefore - whilst it may draw attention, to state categorically that there was absolutely no DNA of LM at the crime scene, it is in fact a false statement to make - The correct statement to make is - There was no conclusive DNA of LM's at the crime scene that could signify without a doubt that he was the murderer, that it had been left at the time of this girls death.

There is a massive difference between those two statements. CD  was in fact correct - there was no stranger DNA that could point this murder to being that of An another. Albeit the endless debate around SK's DNA. When Jigsawman alias was around the DNA being touted out was nothing short of horrendous - that there were up to 20 different male profiles.

And to date there is still none - there was further testing done by the SCCRC in 2014. They obtained one further partial profile from the trousers I believe.

[Chris_Halkides]

And that my understanding is that multiple partial profiles were obtained out with that of a full profile? With a significant amount of locus with alleles attributable to LM. Not the amount required, conclusively to say that they were his.
SNIP
Therefore - whilst it may draw attention, to state categorically that there was absolutely no DNA of LM at the crime scene, it is in fact a false statement to make - The correct statement to make is - There was no conclusive DNA of LM's at the crime scene that could signify without a doubt that he was the murderer, that it had been left at the time of this girls death.

What evidence exists which supports what you wrote in these two paragraphs?

I have been reading more on the interpretation of DNA mixtures.  In Jane Moira Taupin's book Introduction to forensic DNA evidence for criminal justice professionals, she lists the criteria for a straightforward interpretation of a DNA mixture on page 96:

"The DNA comes from only two sources.
The two sources are unrelated.
The ratio of the amount of DNA contributed by each of the two sources is adequate for interpretation of both sources.
The appropriate amount of DNA was amplified and the alleles for both sources exceed the analytical threshold of the laboratory.
No degradation, inhibition, or primer variants are present to affect peak heights and the apparent DNA ratio.
All stutter peak sand other artifacts are below the analytical threshold or clearly distinguishable as artifacts."

Given what Ms. Ure said, there must have been at least three contributors. Without more information one cannot say much about the other five criteria.

[Holly Goodhead]

http://news.bbc.co.uk/1/hi/scotland/4098795.stm

[Chris_Halkides]

Thank you for providing the link.  This is the same story from which I quoted upthread.  Here is an additional sentence of relevance to the DNA found on the bra.  "She [Ms. Ure] said: 'We could tell there was some male DNA present but we couldn't tell whether one or both of the second individuals were males.'"

I surmise that the deconvolution of the mixture into contributors was not complete, but I am not sure.

[Holly Goodhead]

Thank you for providing the link.  This is the same story from which I quoted upthread.  Here is an additional sentence of relevance to the DNA found on the bra.  "She [Ms. Ure] said: 'We could tell there was some male DNA present but we couldn't tell whether one or both of the second individuals were males.'"

I surmise that the deconvolution of the mixture into contributors was not complete, but I am not sure.

Hi Chris, I think we met on the IA forum/Bamber? 

As far as I can see there's not much by way of reliable info in the public domain.  I would suggest contacting Sandra Lean and see if she will share the info (I think she has) that pertains to the DNA evidence from the forensic scientist.

I've been referring to a couple of court of appeal docs:

https://www.scotcourts.gov.uk/search-judgments/judgment?id=26ab8aa6-8980-69d2-b500-ff0000d74aa7

https://www.scotcourts.gov.uk/search-judgments/judgment?id=e2988aa6-8980-69d2-b500-ff0000d74aa7

[William Wallace]

I appreciate it's irrelevant, i just wondered why so many people still say there was NO dna found and use it as the basis of their belief that he's innocent. if it were more widely known that there WAS evidence, it was just decided to be discounted due the nature of their relationship, i would have thought that might shut a lot of them up lol.

There is an explanation for this.      Read this from the Trial regarding DNA found on Jodi:

"The court heard forensic teams had spent 18 months examining hundreds of items, including clothing from Luke Mitchell, in a bid to find DNA clues as to the murderer's identity.

Tayside Police forensic scientist Susan Ure spoke about the work carried out comparing bloodstains found at the murder scene and other reference samples, taken from members of her family and Luke Mitchell.   "Ms Ure said a stain on a bra Jodi had been wearing showed DNA traces from more than two individuals - some of which matched parts of Luke Mitchell's genetic profile".

She said: "We could tell there was some male DNA present but we couldn't tell whether one or both of the second individuals were males."

In otherwards when a profile matches parts of someone's DNA and only parts, those parts are often identical to 50% of the population, so a partial DNA match means they could share those parts with 30 million other people in the UK. Partial DNA matches thus are worse than useless. Hence they couldn't even say for sure the profiles were male or female.

So the answer to your question is simple. There was no DNA on Jodi at all that could be confirmed as belonging to Mitchell.

As for the story that SK's DNA including sperm got on Jodi's t-shirt because she'd borrowed it? What a load of utter hogwash. Now..............at first there was this T-shirt, then it was one of an identical pair but the 2nd one was "missing". Then weeks later, the 2 t-shirts became "several" which conveniently erases the question about one being "missing", because "several" does not mean 2. Several would generally be viewed as 4 or 5 or more. HEY PRESTO !! The missing number 2 t-shirt is no longer "missing" !!

I have to leave it to your imagination to solve the "t-shirt mystery" because I can't expand on possibilities on here.

I can tell you one thing though, the story about Jodi borrowing a t-shirt which had SK's sperm and DNA on it not only sounds like a load of utter hogwash, it is.