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  1. #1
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    I talk with a DNA expert

    Some preliminary comments. My "expert" will remain unidentified, except to reveal she's female. She is not famous, she does not serve as an expert witness in court - though she could. She does DNA testing on a daily basis, so presumably she knows quite a bit about it.

    A second point - I don't know squat about dna, or any other scientific stuff, so there's really no point arguing with me if you disagree with anything I'm going to say. My only possible response is "That's what I was told". I'm just a reporter. (and not even a science reporter)

    A final preliminary matter - my expert doesn't know anything about legal standards of evidence admissability. She's just giving me the scientific point of view.

    This is what I was told.

    1. There is no male/female dna. IOW, a sample of dna can't reveal whether it was from a man or a woman. Think of it somewhat like fingerprint lines - unique to the individual, but not M/F. My expert did say that chromosomes could reveal M/F origin, but not dna. So, all this business about male dna being left in the panties/longjohns is not proven. We know it's a match, but we don't know if it's male or female.

    2. DNA does not degrade over time. Cells degrade, but the dna is still intact. My expert said she could analyze a sample 1000 years old, if you have one. Which brings us to markers.

    3. My expert had no idea what I was talking about when I asked about markers. She said chromosomes have markers, but not dna. I asked if maybe the bands were being called markers, and she said she tought that might be what non-scientists were talking about. In her opinion, it wouldn't matter how many bands were present, she could say yes/no as to a match.

    We learned from Brent Turvey last night that as few as 7 markers have been sufficient to go to court (whatever a marker is)

    4. Sample size is not an isssue. She laughed about the distinction between lcn and "normal" dna sample sizes and tests. She said she could do a test with one cell. She said in the field they've been able to amplify a sample that small and analyze it for about 30 years, so she didn't really know what was supposed to be "new" about this lcn test.

    Since sample size (one cell or more) isn't an issue in gettng a match, she said that there was no way to determine whether the sample from the longjohns was "big" based on it being run as a "normal" test. One cell is all it takes.

    5. Someone knows whether the panty dna was semen, blood, or saliva. She said they'd be able to tell from other material in the cell what sort of liquid it came from.

    6. The three dna samples could have got there by some inocent transfer. My expert saw no reason to conclude that the dna had to be from the killer, or was even highly likely to be from the killer. She didn't think the liquid/skin cell dichotomy mattered much, as only one cell is required for anlaysis (though typically there is more than that), and there are many scenarios by which both liquid and skin could transfer - sneezing, coughing, wiping her down after going to the bathroom, can all cause a liquid transfer and at the same time skin cell transfer. Again, there needn't have been any "large" sample present - a 3 point match requires only 3 cells.

    I think that is all I asked her about. If I remember anything else I'll add it in another post.

    Again, I want to point out that my expert knows how to work with DNA, but not about courts standards of admisibility or how to present the evidence to a jury.

  2. #2
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    Very interesting post. Thanks, Chrishope.


    Now if someone with some knowledge about DNA will stop by & respond.

  3. #3
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    I should say that my own ignorance makes understanding this stuff difficult. The problem is compounded slightly by the fact that the expert is not a native english speaker.

    One thing we have cleared up in the past hour or so is that she makes a distinction between dna and chromosomes. I have a feeling that many in the legal profession use the terms as rough synonyms.

  4. #4
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    Wouldn't surprise me.
    I'm as mad as HELL and I'm NOT gonna take it anymore!.

  5. #5
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    I have to be honest Chrishope. The research I have seen seems to contradict most of the things that your expert claims.
    Quote Originally Posted by Chrishope View Post
    1. There is no male/female dna. IOW, a sample of dna can't reveal whether it was from a man or a woman. Think of it somewhat like fingerprint lines - unique to the individual, but not M/F. My expert did say that chromosomes could reveal M/F origin, but not dna. So, all this business about male dna being left in the panties/longjohns is not proven. We know it's a match, but we don't know if it's male or female.
    " Nuclear DNA STR analysis can identify the gender of an individual." http://www.dps.state.ak.us/crimelab/services/DNA.aspx

    Can you name one expert on either side of the issue that has said that the gender of the pantie's DNA donor was unknown?

    Quote Originally Posted by Chrishope View Post
    3. My expert had no idea what I was talking about when I asked about markers. She said chromosomes have markers, but not dna. I asked if maybe the bands were being called markers, and she said she tought that might be what non-scientists were talking about. In her opinion, it wouldn't matter how many bands were present, she could say yes/no as to a match.
    Thats strange that she has never heard of genetic markers. Ask her about LOCI and VNTR. Here is a Wikipedia article about genetic markers (I know that wikipedia isn't necessarily that accurate, but I don't particulary want to spend the time to dig up a scholary journal etc.) http://en.wikipedia.org/wiki/Genetic_markers

    Quote Originally Posted by Chrishope View Post
    We learned from Brent Turvey last night that as few as 7 markers have been sufficient to go to court (whatever a marker is).
    They got about 10 markers with the DNA on the panties.

    Quote Originally Posted by Chrishope View Post
    4. Sample size is not an isssue. She laughed about the distinction between lcn and "normal" dna sample sizes and tests. She said she could do a test with one cell. She said in the field they've been able to amplify a sample that small and analyze it for about 30 years, so she didn't really know what was supposed to be "new" about this lcn test.
    "LCN testing allows genetic profiles of offenders to be created from very small tissue samples that have only been detectable with new techniques available since 1999." http://www.geneticsandhealth.com/200...controversial/

    "The possibility of having inaccurate test results increases if a very small sample of DNA is available for testing." http://www.cigna.com/healthinfo/hw4439.html



    I'll talk more about the transfer later...

  6. #6
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    I thought chromosomes are what contain the DNA? I don't see how there can be dna without it in the cell. Maybe the expert was being literal and it is interesting. I want to learn more about this testing.
    Last edited by txsvicki; 07-14-2008 at 02:46 AM. Reason: correct

  7. #7
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    Quote Originally Posted by Chrishope View Post
    Some preliminary comments. My "expert" will remain unidentified, except to reveal she's female. She is not famous, she does not serve as an expert witness in court - though she could. She does DNA testing on a daily basis, so presumably she knows quite a bit about it.
    On what basis do you think she could serve as an expert witness in court? My brother has been qualified as an expert witness for DNA testimony, although his day job is as a chief researcher who works with DNA on a specific genetic disease. His big court adventure is a long story but he was indeed qualified as an expert.

    In my brother's lab, there are several lab workers who do a lot of the work but they're certainly not experts on DNA itself.

    1. There is no male/female dna. IOW, a sample of dna can't reveal whether it was from a man or a woman. Think of it somewhat like fingerprint lines - unique to the individual, but not M/F. My expert did say that chromosomes could reveal M/F origin, but not dna. So, all this business about male dna being left in the panties/longjohns is not proven. We know it's a match, but we don't know if it's male or female.
    DNA is the building block of chromosomes. Think of chromosomes as a long, long banner that carries a message. DNA is the "alphabet" that is used to write that message. In that sense, she's correct--there is no such thing as male/female DNA.

    However, there are definitely male/female chromosomes and they are carried in every single cell of the body--they're called the X and Y chromosomes. Women are XX, men are XY, meaning that men have one copy of the X chromosome and one copy of the Y chromosome.

    2. DNA does not degrade over time. Cells degrade, but the dna is still intact. My expert said she could analyze a sample 1000 years old, if you have one. Which brings us to markers.
    Sort of. DNA itself doesn't degrade but chromosomes do. Remember those long banners I mentioned above? The letters can fall off the banners. Once the letters fall off, they still exist but they are no longer readable or useable to form chromosomes.

    3. My expert had no idea what I was talking about when I asked about markers. She said chromosomes have markers, but not dna. I asked if maybe the bands were being called markers, and she said she tought that might be what non-scientists were talking about. In her opinion, it wouldn't matter how many bands were present, she could say yes/no as to a match.
    She's literally true--DNA does not have markers. The markers are formed by the four "letters" that comprise the DNA alphabet. However, most non-science reports use the terms DNA and chromosomes interchangeably.

    4. Sample size is not an isssue. She laughed about the distinction between lcn and "normal" dna sample sizes and tests. She said she could do a test with one cell. She said in the field they've been able to amplify a sample that small and analyze it for about 30 years, so she didn't really know what was supposed to be "new" about this lcn test.
    Here again, she's both right and wrong. Yes, they've been able to test for the presence of DNA for over 30 years. No, they have not been able to test single cells for chromosomes until about 5-7 years ago.

    The chromosomes (the banners and the order of the letters they carry) are what is important in criminal court. If all they could test for was DNA, then all that could be testified to in court would be that "yes, this whitish residue is from some type of animal, rather than being mineral or plant in nature." The type of animal couldn't even be identified just from the presence of DNA; it takes chromosomes in order to identify the type of animal.

    Since sample size (one cell or more) isn't an issue in gettng a match, she said that there was no way to determine whether the sample from the longjohns was "big" based on it being run as a "normal" test. One cell is all it takes.
    One cell is all it takes in order to ascertain the presence of deoxyribonucleic acid (DNA) but until fairly recently, it took many more than a single cell in order to test for the structure of the chromosomes. And the chromosomes are what count in court.

    Tangential note: I just realised that the reason the term DNA is used rather than the more accurate term chromosomes is probably because DNA is much easier to type and say than the word chromosome.

    In order to run the routine test, it takes a minimum sample size of 50 cells. The LCN (low count number) DNA test can be done with as little as a single cell.

    6. The three dna samples could have got there by some inocent transfer.
    Probably not. The number of cells found in each patch tested (they tested at least two different patches on the longjohns) makes it unlikely that it was secondary transfer. Secondary transfer is usually very few cells--5 to 20 or so. For there to have been a minimum of 50 cells present in each of two locations on the longjohns makes it very unlikely to have been secondary transfer.

    My expert saw no reason to conclude that the dna had to be from the killer, or was even highly likely to be from the killer. She didn't think the liquid/skin cell dichotomy mattered much, as only one cell is required for anlaysis
    She is factually wrong; the tests they actually did require a minimum of 50 cells per test.

    Again, there needn't have been any "large" sample present - a 3 point match requires only 3 cells.
    Factually wrong--a 13 point match can be made from a single cell using LCN DNA testing. They did not use the LCN DNA test because they got sufficient cells from each location to run the routine test. The number of points matched is not dependent upon the number of cells in the sample but the likelihood of secondary transfer vs primary transfer is determined in part by the number of cells found.

  8. #8
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    Probably not. The number of cells found in each patch tested (they tested at least two different patches on the longjohns) makes it unlikely that it was secondary transfer. Secondary transfer is usually very few cells--5 to 20 or so. For there to have been a minimum of 50 cells present in each of two locations on the longjohns makes it very unlikely to have been secondary transfer.
    Could they have been the source of the secondary transfer? I'm serious.

    Remember, this DNA evidence would mean more to me if there were actual evidence of a fifth person in the house that night. Mary Lacy has ignored, or is just plain unaware of, so much evidence in this case (which is how we wound up with Mr. Karr to start with), and has focused on this DNA so much (when most of the original investigative team--you know, the people who actually investigated the case and gathered the evidence--didn't think it was anything to get excited about), that it's hard for me to jump on the bandwagon. (But then, I'm a big guy, so I'd break the wheels!)
    I'm as mad as HELL and I'm NOT gonna take it anymore!.

  9. #9
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    What's not clear to me is this:

    They're scraping BOTH sides of the waistband in hopes of finding a cell to test.....


    Did they scrape & then TEST each side separately?

    How do scientists determine skins cells can't transfer from one area of clothing to another when it's been folded & sealed into an evidence bag?

  10. #10
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    Quote Originally Posted by Chrishope View Post
    1. There is no male/female dna. IOW, a sample of dna can't reveal whether it was from a man or a woman. Think of it somewhat like fingerprint lines - unique to the individual, but not M/F. My expert did say that chromosomes could reveal M/F origin, but not dna. So, all this business about male dna being left in the panties/longjohns is not proven. We know it's a match, but we don't know if it's male or female.

    4. Sample size is not an isssue. She laughed about the distinction between lcn and "normal" dna sample sizes and tests. She said she could do a test with one cell. She said in the field they've been able to amplify a sample that small and analyze it for about 30 years, so she didn't really know what was supposed to be "new" about this lcn test.

    Since sample size (one cell or more) isn't an issue in gettng a match, she said that there was no way to determine whether the sample from the longjohns was "big" based on it being run as a "normal" test. One cell is all it takes.
    .
    Re male and female determination, definitely untrue
    http://www.thenakedscientists.com/HTML/content/interviews/interview/477/
    http://www.cstl.nist.gov/biotech/strbase/Amelogenin.htm

    Also, regarding single cell testing, doubtful whether it happens in real world forensics, and I would certainly hate to be in court trying to sell a case based on it.
    “It saddens me that 20 years after my sister Nicole’s murder, we are still seeing the same crimes, just different names, over and over again.”
    - Denise Brown (sister of Nicole Brown Simpson)


  11. #11
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    Quote Originally Posted by LI_Mom View Post
    What's not clear to me is this:

    They're scraping BOTH sides of the waistband in hopes of finding a cell to test.....


    Did they scrape & then TEST each side separately?

    How do scientists determine skins cells can't transfer from one area of clothing to another when it's been folded & sealed into an evidence bag?
    I think we're going to see all kinds of LE problems in the next few years regarding transfer DNA.

    How often does it happen really? There have been so few tests on transfer DNA that it seems no one really knows.

    Would the presence of transfer DNA from JonBenet's parents make it more or less likely that this DNA is from the killer?

    What's going to happen in the future for cases where there is strong circumstantial evidence of a person's guilt but there is unknown DNA from one or two individual skin cells on the victim?

  12. #12
    Jayce, thank you for responding to Christope, apparently who ever he spoke with is NOT a DNA expert by any means otherwise they would be familiar with terms like markers.

    I work and have always worked in the Biotech industry. I reported what a top Scientist here had to say about this recent find. He said it is significant because this "Touch DNA" really a fancy word for low profile testing, was important because of where it was found on the long johns and seemingly matches that found in her panties. Pretty hard to "plant" this type of DNA when it was mixed with JB's own blood in her panties. Keep in mind this doesn't mean it necessarily belongs to the killer and is just one more piece of the puzzle to keep in mind. Please keep in mind a famous cold case murder which I mentioned on this board (probably years ago), where the woman's pantyhose were tested and yielded 2 foreign sets of DNA. One belonging to a serial rapist who was already serving time in prison and another to a family man, who had no criminal record. The family man was convicted of the crime, because the DA could show a correlation to the woman, his proximity of the crime, etc. The man had never committed another crime since and was a devoted father. What I found incredible was the other DNA found on the woman's pantyhose that had belonged to the serial rapist. He would have been 5 years old at the time, and obviously not capable of the crime. Another thing was he lived miles from the woman. It was never explained how this 5 year olds DNA got on the pantyhose of the murder victim. We have NO idea the age of this foreign DNA, and Mary Lacy is a complete imbecile for publicly apoligizing to the Ramseys. What she should be doing is apologizing to the citizens of Boulder for doing such as lousy job filling her term in office. She should be thrown out of her position with a swift kick in the ass.

    This is MALE DNA that was found in a place where it shouldn't be. I'd like to know how much and if they found Patsy's touch DNA on those long johns as well.

  13. #13
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    Thanks for keeping us on the straight and narrow, Ned.
    I'm as mad as HELL and I'm NOT gonna take it anymore!.

  14. #14
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    Yes, good point. Lacy makes a big show about the male DNA that was found, stays mum about whether any one else's was also found there, or whether any other items have been tested. That speaks volumes to me about what was actually found.
    THIS time, we get it RIGHT!

    This post is my constitutionally-protected opinion. Please do not copy or take it anywhere else.

  15. #15
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    Quote Originally Posted by SuperDave View Post
    Could they have been the source of the secondary transfer? I'm serious.
    I'm not sure who or what you mean when you say "they". If you're asking whether the two patches of DNA they tested could have transferred DNA to other surfaces, it's possible. It depends on the structure of the fabric and the "stickiness" level of the skin cells involved (some skin cells are stickier than others).

    I *often* wish English had a third person gender-neutral pronoun for humans and a gender-neutral pronoun for inanimate objects.

    Remember, this DNA evidence would mean more to me if there were actual evidence of a fifth person in the house that night. Mary Lacy has ignored, or is just plain unaware of, so much evidence in this case (which is how we wound up with Mr. Karr to start with), and has focused on this DNA so much (when most of the original investigative team--you know, the people who actually investigated the case and gathered the evidence--didn't think it was anything to get excited about), that it's hard for me to jump on the bandwagon. (But then, I'm a big guy, so I'd break the wheels!)
    I think more of the evidence from the case needs to be tested, for sure.

    I think Mary Lacy was handed a pig of a case. When Karr poppped up, I don't think there's any course of action she could have taken that would have made everyone happy. If she'd had the Thai police swab him and send in the swab, I doubt anyone would have accepted that. Sending someone out to follow Karr around until he discarded something that might carry his DNA could open questions as to the purity of the sample and since he was obviously aware he was under surveillance, he probably would have tried hard not to discard any possible sources of DNA.

    Without the DNA, his alibi amounted to his ex-wife and her family saying he was at their place for Christmas.

    This has turned into one of those situations where no one is happy, no one is satisfied but there's never quite enough evidence to make a decision beyond a reasonable doubt in either direction.

    For instance--if they found Patsy Ramsey's DNA on the longjohns... so what? It is known she touched them innocently. If they didn't find Patsy Ramsey's DNA, again, so what? There are so many legitimate reasons for there to be a lack of transfer DNA, it doesn't mean anything when you're talking about a family member.

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