DNA Fingerprinting - Simpson Trial

U27111 at uicvm.uic.edu U27111 at uicvm.uic.edu
Mon Feb 20 04:51:16 EST 1995


Hi, this is a discussion going on in the alt.fan.oj-simpson
newsgroup.  I am cross-posting it here because I am not a forensic
science specialist and frankly, could use some help here. Please
feel free to jump in and give your own opinions or share some
knowledge?

Thank you,

-Kathy

**********************************************************
KR>>> Did you know that the inventor of the main DNA test that the
KR>>> prosecution is carrying out, namely PCR, is testifying for
KR>>> the defense?  He won a Nobel Prize for his invention.  The
KR>>> prosecution is gonna get f----d! You can only argue so much
KR>>> with the damn inventor!  DNA IS NOT A FINGERPRINT!

HFC>> Ken, I think Kary Mullis will argue that DNA does lie.  He
HFC>> will argue that the amplification is so large that minor
HFC>> contamination can produce false positives.
HFC>> The defense will attack collection and handling and will say
HFC>> that positives are old, planted, or contaminants.

1.   Mullis did indeed invent PCR (by accident I may add), but he
     did not develop it for clinical use, let alone for the
     forensic sciences.

2.   As for being a Nobel laureate... I have several opinions on
     this one.

First:  I don't believe receiving the Nobel means as much as it may
once have.  Especially when looking at the likes of David Baltimore
and *almost* Dr. Robert Gallo!  I suggest as book titled "Nobel
Prize Women in Science" by Sharon Bertsch McGrayne, published 1993
by Carol Publishing Group... if you want to read about the greed,
politics and ego involved?

Second:  As far as Mullis being a Nobel laureate...

For what ever being a laureate is worth anymore... I personally
tend to believe that he has abused this position anyway in siding
with Duesburg in the HIV is NOT the cause of AIDS debate.  By being
one-sided and obviously loosing his objectivity... he has used his
status to promote this debunked theory.  I find this to be totally
irresponsible, especially in the face of our modern plague (see
"The Coming Plague" by Laurie Garrett, pp.383).  In addition, see
D.D.Ho et al., Nature 373, 123 (1995) and X.Wei et al., Nature 373,
117 (1995)... which so far as I have read, neither Duesburg or
Mullis has responded to.

Thus, I think his involvement in this debate has indeed seriously
effected his credibility... at least as far as I am concerned.  I
also tend to doubt any of this would be brought up in front of the
jury, or even if it was, that they would even understand the
complexities of such a debate?

3.   False Positive Contaminations:

     False positive contaminations in PCR can only come from poor
     laboratory procedures... they would NOT come from collecting
     and handling procedures.

     And running a blank internal sample would help to detect such
     a possible problem (result).

JK> 1. If it is an RFLP test, where did the DNA that's restricted
JK> come from?  If from a PCR reaction, in my opinion it can be
JK> discarded. It could just as easily be from contamination, and
JK> in all likelihood is.

How's that if it's a positive result with negative internal
controls?

JK> If you want to follow it though, then you have to ask a lot of
JK> other questions.  How many regions of the genome did they
JK> amplify and how many restriction enzymes did they use? Almost
JK> more importantly, WHAT regions did they use? There are
JK> multitudes of genomic regions that are identical between the
JK> vast majority of humans and even between humans and plants,
JK> fungi, fish, you name it. Provided the regions are appropriate,
JK> ** did they use sufficient numbers of enzymes ** to even come
JK> close to knowing if there is a "match"? I think every protocol
JK> I've heard has mentioned only 5 enzymes.

This isn't a research lab where people toss things together and see
what they get?  This is a fairly standardized procedure where all
labs look at the same regions.

BTW, also unlike research labs... these labs and techs are
certified.

Thus, if this was even ten years ago... I would have agreed with
your argument... but not today.

JK> 2. The second RFLP, aka fingerprinting, is to use only DNA
JK> (blood/hair) from the crime scene and cut it with a restriction
JK> enzyme. You electrophorese it on a gel which gives what's
JK> called a smear. It is essentially a line of continuously
JK> varying sizes of DNA. You then probe the dried gel with various
JK> DNA sequences. The probes will stick only to those sequences
JK> occurring in the genome. There are, in fact, a few probes that
JK> appear to be individual specific. HOWEVER!! This again must
JK> be done under very stringent conditions. Under some conditions,
JK> only MOST of the sequence must match for the probe to attach
JK> (this applies to the PCR method as well, by the way). In this
JK> case, you are calling it a match when it is not, and for some
JK> uses in population biology it is perfectly acceptable. In
JK> forensics, hanging a murder conviction on someone's head, it is
JK> absolutely not acceptable. So, EVEN if a "match" is what the
JK> prosecution comes up with, if the conditions were loose enough,
JK> it might have matched you or me as well.

Well again you are totally ignoring the fact this is now a
certified, standardized field with specific parameters in which
they have to work under.

And as for the population genetics argument...see "DNA
fingerprinting dispute laid to rest" by Lander and Budowle in
Nature (371), pp.735- .

And as for hanging a murder conviction based upon these tests...
Well, I think no matter what number they come up with in the end
(1:10,000 to 1:50,000?)... how many of these 10,000 - 50,000
'other' possibilities lived in that area, had victim's blood in
their car, a bloody glove on their property, a bloody sock in their
bedroom and a cut finger on the same side as the bloody footprints
walking away from the murder scene?

That's how you hang a murder convention on somebody's head.

>Bottom line: The test results count ONLY if everything was done
>correctly. It wasn't even close to correctly in the prelim.

They had yet to do DNA testing at the time of the PreLim... that
was all serological test results presented at that point!

>But now that we have hotshot labs involved it will be up the
>experts on both sides to battle it out and enlighten us. Of course
>the most difficult part of all of this is how to convey the
>information to people not fluent in DNA methodologies so that they
>are even able to make informed conclusions. (sigh)

Here I totally agree with you!

JK> P.S. And now you know why I am so adamantly opposed to everyone
JK> jumping to conclusions based on various leaks or Marsha peeing
JK> in her pants to let the world know she has match, she has
JK> match! Only time will tell whether her match is even remotely
JK> valid.

Well... how would explain several 'different' samples all having
the same 'match' if there were not indeed valid?  I mean, you could
use this argument of yours if there was only 1 or 2 single
samples... but apparently, these results have come out the same for
each and every sample tested by both RFLP and PCR, in a few
different labs (Department of Justice as well as CellMark).

You can argue false positives, contamination and what-have-you...
but on ALL the samples from both locations?  Again, that would
bring you back to a collecting and handling problem to question
it's validity...  and a collecting and handling problem would NOT
give you false positives.

-Kathy





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