Why the DNA may NOT be important

[Anti-K]

A far better question is, why this skilled criminal took his gloves off or never wore any to commit this crime.

It has been proposed that the killer wore gloves, but removed them so that he could have skin-to-skin contact with the victim during the sexual assault.
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AK

 

[Anti-K]

Well, seeing as how unsterilized nail clippers were used on her body, who knows?

Failure to match DNA from the 8 autopsies prior to Jonbenet’s make the issue of the clippers moot. And, the most that this should throw into question is the DNA found beneath the fingernails.
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AK

 

[Anti-K]

Where does the information about the nail clippers come from?

In their books, Schiller, Thomas and Kolar all mention the possibility that Meyer made some error in his use of the clippers. A lot of the reportage said the same thing, but I’m not sure that anyone’s ever stated it as fact, and iirc there is small dispute as to whether the same clippers were used per nail, or the same clippers were used as from a previous autopsy, or the clippers were simply unsterilized. I don’t recall anyone associated with the investigation ever denying the claim so I tend to think that there there could have been some failure to follow protocol with the clippers, but I’m not convinced as to what impact this had. And, I think that the CODIS/tDNA samples render this a virtual non-issue.
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AK

 

[DeeDee249]

In their books, Schiller, Thomas and Kolar all mention the possibility that Meyer made some error in his use of the clippers. A lot of the reportage said the same thing, but I’m not sure that anyone’s ever stated it as fact, and iirc there is small dispute as to whether the same clippers were used per nail, or the same clippers were used as from a previous autopsy, or the clippers were simply unsterilized. I don’t recall anyone associated with the investigation ever denying the claim so I tend to think that there there could have been some failure to follow protocol with the clippers, but I’m not convinced as to what impact this had. And, I think that the CODIS/tDNA samples render this a virtual non-issue.
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AK

I believe I have seen that Coroner Meyer himself admitted the clippers were not sterilized between autopsies. Proper procedure requires there be 10 sterile clippers - a sterile clipper for each finger. Not only did Meyer use the same clipper for all 10 fingers, he used the same clipper for multiple decedents. I guess nail clippers were rare and expensive in Boulder...

 

[Anti-K]

I believe I have seen that Coroner Meyer himself admitted the clippers were not sterilized between autopsies. Proper procedure requires there be 10 sterile clippers - a sterile clipper for each finger. Not only did Meyer use the same clipper for all 10 fingers, he used the same clipper for multiple decedents. I guess nail clippers were rare and expensive in Boulder...

I don’t recall Meyer admitting it, but I’ve forgotten all sorts of things (and, missed a few!). It doesn’t matter; like I said the CODIS/tDNA samples render this a virtual non-issue.
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AK

 

[THE BUNK]

Question I have for the DNA experts

If the DNA is in degraded condition , then the DNA may never match it's originator, correct?

Also considering how often people touch things in their daily life, the fact that only touch DNA was found makes it even likelier that it was the result of casual contact, correct?

 

[Venom]

I don’t recall Meyer admitting it, but I’ve forgotten all sorts of things (and, missed a few!). It doesn’t matter; like I said the CODIS/tDNA samples render this a virtual non-issue.
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AK

May I ask how so? Isn't it possible that the samples in CODIS could be DNA from someone else that the clippers were used on? How can contamination be completely ruled out.

 

[Anti-K]

Question I have for the DNA experts

If the DNA is in degraded condition , then the DNA may never match it's originator, correct?

Also considering how often people touch things in their daily life, the fact that only touch DNA was found makes it even likelier that it was the result of casual contact, correct?

I’m NOT a DNA expert! But...

Degraded DNA is fragmented DNA. The DNA is breaking down, usually because of environmental factors. Handling it can cause it to break down. When they process DNA they break it down in a controlled fashion. Degraded DNA breaks down in a random fashion. Degraded DNA can provide a full profile, a partial profile, or no profile. It just depends on where the breaks are. Any of the targeted fragments still intact will provide readable results.
.

The DNA will match someone. And, it could match more than one someone (depending on number of markers in a sample). If we use the FBI’s frequency rate of 13.66 than one in every 475,612.75 people could match a FIVE marker sample. Boulder had a population of about 300,00 in 1996/97. 10 markers (out of 13) gives us 1 person in every 226,207,496,572.73.
.

It is not true that only tDNA was found. The fingernails and panty/CODIS samples were not tDNA.

Investigators want to avoid areas where trace evidence is likely to have been the result of casual contact. So, it isn’t about the quantity of DNA, it’s about the location where it was found. We know that the killer was in the little girl’s panties, and we know that he was almost certainly the last person inside her panties, and we know he had to pull down and pull up her leggings to get in there. Could he have left trace evidence during those acts? Of course he could have. How much? There are no rules. It isn’t the quantity, it’s the location.
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AK

 

[Anti-K]

May I ask how so? Isn't it possible that the samples in CODIS could be DNA from someone else that the clippers were used on? How can contamination be completely ruled out.

Contamination is DNA inadvertently introduced to a crime scene sample between the time it is collected and its final analysis. Contamination happens, but it is usually (almost always) discovered. One of the ways that they are discovered is through finding a match – someone associated with the collection, handling, processing, etc, sometimes another unidentified sample being processed in the lab at the same time. Protocols are in place, steps are taken not just to prevent contamination, but to detect it.

Besides that, in this case we know that the DNA from previous autopsies and persons associated with the investigation were compared; this makes the possibility that the CODIS/tDNA samples are the result of contamination very remote.

Since the CODIS sample and the tDNA samples were processed by different labs and were found on separate articles of clothing, one sample mixed and commingled in blood and the others not, one sample on the inside crotch, two on the outside sides, and the possibility that the DNA transferred from one article to the other becomes very remote.

So, the tDNA samples confirm the CODIS sample; and, the CODIS sample confirms the tDNA samples. Technically speaking, contamination can never be completely ruled out, but, in this case we can with confidence provisionally rule it out.
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AK

 

[THE BUNK]

I’m NOT a DNA expert! But...

The DNA will match someone.

Gotcha.

 

[Anti-K]

Just to clarify: the DNA does match someone; we may never know who that someone is.
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AK

 

[BOESP]

A very interesting article here on how to interpret DNA findings:

http://plus.maths.org/content/os/issue55/features/dnacourt/index

 

[ScarlettScarpetta]

We all know how DNA works. And why it is so important to cases. What we know is that more than ever DNA has a bigger role as time passes and it can be dissected and analyzed in smaller samples.

DNA is vital in this case.

 

[bettybaby00]

Really? I wasn't aware this is a forum of DNA experts. I certainly would never presume to be one...maybe that's just me.

In fact I found the section: "How not to use DNA profile evidence" particularly informative, which immediately brought to mind Dr. Krane's warning when asked about the sample in this case....

at the present time there is no generally accepted means of attaching a statistical weight to a mixed DNA profile where drop-out may have occurred [...]you can’t admit it as evidence. It is not something that can be presented to a jury because they simply won’t know what weight to give it if you can’t attach a reliable statistical weight. So, absent a statistical weight all that can really be said is, about a mixed sample where drop-out might have occurred, is that the test results are inconclusive.

Also of note from the article...

"Considering the profile in isolation..."

IMO without a match--which conceivably might never happen--or any other sign of an intruder, it needs to be considered relative to ALL the other aspects of the case. We can't ignore the fact that it's useless in a court of law as it stands right now.

It's ironic that in the example used in the article a man was convicted b/c of faulty DNA reasoning and analysis, yet he may very well have been innocent.

The article sums it up quite well...

What's problematic is not so much that people don't appreciate the problems, (with DNA) that is the case in many fields. The real difficulty is that people don't appreciate that they don't appreciate the problems — they don't even realise that there is a problem. It all looks so straightforward, instead of incredibly subtle. The correct computations needed to understand statistical evidence such as DNA profile matches are not mathematically difficult, it's simply arithmetic. But knowing what the correct computations are is something that is not many people understand.

Anyway, thanks BOESP for an interesting and easy to understand article.

Signed me: someone who always appreciates relative information

 

[Aleph]

If the DNA did come from the rumored Malaysian factory worker, wouldn't the DNA itself tell us at least that it had been an Asian person handling it?

 

[bettybaby00]

If the DNA did come from the rumored Malaysian factory worker, wouldn't the DNA itself tell us at least that it had been an Asian person handling it?

At this time I don't believe this is possible. From what I understand some say an "educated guess," is possible, but I don't believe they are talking about testing a mixed, partial profile sample which is what we've got in this case.

It's also important to consider that if they were able to say with any sort of certainty, what race this sample indicated--or doesn't indicate, ie, a person from Malaysia--that it would have been reported on...and I don't mean issued as a statement by LW.


*please note I am by no means an expert, but google is my friend

 

[Tawny]

It's painfully clear "we all" DON'T actually know how DNA works like "we" seem to believe "we" do.

 

[otg]

It's painfully clear "we all" DON'T actually know how DNA works like "we" seem to believe "we" do.

Thanks, BOESP, for an informative article.

I agree with your statement, Tawny. The referenced article says as much in its concluding paragraphs (bbm):

Unfortunately there are still few jurors, lawyers and judges who understand the statistical subtleties of such evidence. (snip) What's problematic is not so much that people don't appreciate the problems, that is the case in many fields. The real difficulty is that people don't appreciate that they don't appreciate the problems — they don't even realise that there is a problem. It all looks so straightforward, instead of incredibly subtle. The correct computations needed to understand statistical evidence such as DNA profile matches are not mathematically difficult, it's simply arithmetic. But knowing what the correct computations are is something that is not many people understand.
​

IOW, it's the classic Dunning-Kruger effect:
http://rationalwiki.org/wiki/Dunning-Kruger_effect

 

[ScarlettScarpetta]

It's painfully clear "we all" DON'T actually know how DNA works like "we" seem to believe "we" do.

Actually the only ones who do not get DNA are the ones here trying to explain how in this case, the only one in history that DNA just doesn't matter.

 

[Mama2JML]

The CODIS DNA profile is not a "mixed partial profile".