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Chris,
Sorry for the late reply. It's been crazy busy lately.
The DNA issue is fairly complex so I'm just going to skim over it at a high level. There's a lot of detail on it earlier in this thread from prior to the independent experts report. Most if not all of the concerns brought up before were validated by the experts.
My basic issue with how the blog treats this is that it doesn't actually give a good overview of the concerns raised by the independent experts or their conclusions and instead focuses on how the results can be rehabilitated to be found acceptable, which is exactly counter to the findings of the report.
Asking "how likely" it is that the DNA was contaminated is simply a non-sensical question. It is always a possibility even under the best of conditions with normal testing which is why there are supposed to be stringent procedures to guard against it.
With LCN DNA testing the danger of contmination is far greater. Because of the greater number of replication cycles even the smallest amount of contanimation will show up in the results. A tiny amount DNA that would not affect the outcome of a test with a significant sample will be a major problem after that many replication cycles. (This is the amplification that he was discussing. It's standard in DNA testing, but in the case of LCN testing it goes on for a greater number of cycles.)
Most courts won't allow the results of even well performed LCN DNA testing. And this wasn't well performed. They don't even meet the basic standards for NON-LCN DNA testing.
The blog tries to open up the possibility that there were adequate controls on the samples in the lab to prevent the possibility of cross-contamination. Unfortunately Stefanoni's record keeping was rather poor (to be generous) so we can't really tell much about the treatment of samples in the lab. We do know however that whatever was done was inadequate for this type of testing.
But let's look at the possibilities a bit...
He makes a point that between Sollecito's flat and the lab that no one who had contact with Kercher's DNA handled the knife. Possibly true. However we do know that both Knox and Sollecito were at the scene of the murder, prior to the collection of the knife. As were some of the officers involved in the collection. (A point that seems to have skipped by the blog author) Knox specifically is known to have had direct contact with Kercher's blood in the bathroom the day after the killing. Given this, the possibility for contamination prior to or during collection is non-trivial considering the small amount of material found.
At the lab itself there was plenty of Kercher's DNA. The author tries to suggest that if control samples were run that it would somehow demonstrate that contamination at this stage was less likely. Given the tiny amounts involved prior to replication that's not the case. (See some of the earlier discussion on this thread) In general the risk of contamination is considered to be so high at the laboratory level that the best practice for LCN testing is to not perform it at a lab that contained the DNA that you're looking for. The machinery should be under slightly higher air pressure than the lab itself to prevent the possibility of airborne contamination. We know of course that wasn't the case here.
For scientific evidence to be acceptable it is supposed to meet certain standards. In this case the independent experts came up with over 50 deficiencies related to the collection and testing of the clasp and knife. That's an astounding number, but it's unlikely to tell the whole story because records were either not provided, not kept or never made on some aspects of the testing itself.
So what is the possibility that it's contamination? According to the court appointed experts it's unnacceptably high. That doesn't give us a quantifiable number, but we do know that there was the potential for it to occur prior to collection, during collection and during testing. The degree of concern that should be applied is hightened by the fact that even the most basic procedures to prevent it were not followed.
Simply watching the tape showing the collection of the clasp should give a good feel for the "care" with which they treated evidence.
I have no issue with people who geniuely believe that Knox and Sollecito had a part in the murder, but when it comes to scientific evidence it's not a subjective thing. The court selected experts said it had no evidentiary value and to try and twist the findings so that there is a loophole where you can still claim the tests are valid and support your position is absurd IMO. And in this particular case the arguments made are misleading at best or dishonest at worst.
The blog author would be much better advised to simply drop the knife and clasp and return to the supposed "mountain" of other evidence.
My apologies for any incoherencies in the post... It was written in 30 second chunks as time permitted this morning. If you have any questions or if you'd like clarification on anything please feel free to ask.
John
Sorry for the late reply. It's been crazy busy lately.
The DNA issue is fairly complex so I'm just going to skim over it at a high level. There's a lot of detail on it earlier in this thread from prior to the independent experts report. Most if not all of the concerns brought up before were validated by the experts.
My basic issue with how the blog treats this is that it doesn't actually give a good overview of the concerns raised by the independent experts or their conclusions and instead focuses on how the results can be rehabilitated to be found acceptable, which is exactly counter to the findings of the report.
Asking "how likely" it is that the DNA was contaminated is simply a non-sensical question. It is always a possibility even under the best of conditions with normal testing which is why there are supposed to be stringent procedures to guard against it.
With LCN DNA testing the danger of contmination is far greater. Because of the greater number of replication cycles even the smallest amount of contanimation will show up in the results. A tiny amount DNA that would not affect the outcome of a test with a significant sample will be a major problem after that many replication cycles. (This is the amplification that he was discussing. It's standard in DNA testing, but in the case of LCN testing it goes on for a greater number of cycles.)
Most courts won't allow the results of even well performed LCN DNA testing. And this wasn't well performed. They don't even meet the basic standards for NON-LCN DNA testing.
The blog tries to open up the possibility that there were adequate controls on the samples in the lab to prevent the possibility of cross-contamination. Unfortunately Stefanoni's record keeping was rather poor (to be generous) so we can't really tell much about the treatment of samples in the lab. We do know however that whatever was done was inadequate for this type of testing.
But let's look at the possibilities a bit...
He makes a point that between Sollecito's flat and the lab that no one who had contact with Kercher's DNA handled the knife. Possibly true. However we do know that both Knox and Sollecito were at the scene of the murder, prior to the collection of the knife. As were some of the officers involved in the collection. (A point that seems to have skipped by the blog author) Knox specifically is known to have had direct contact with Kercher's blood in the bathroom the day after the killing. Given this, the possibility for contamination prior to or during collection is non-trivial considering the small amount of material found.
At the lab itself there was plenty of Kercher's DNA. The author tries to suggest that if control samples were run that it would somehow demonstrate that contamination at this stage was less likely. Given the tiny amounts involved prior to replication that's not the case. (See some of the earlier discussion on this thread) In general the risk of contamination is considered to be so high at the laboratory level that the best practice for LCN testing is to not perform it at a lab that contained the DNA that you're looking for. The machinery should be under slightly higher air pressure than the lab itself to prevent the possibility of airborne contamination. We know of course that wasn't the case here.
For scientific evidence to be acceptable it is supposed to meet certain standards. In this case the independent experts came up with over 50 deficiencies related to the collection and testing of the clasp and knife. That's an astounding number, but it's unlikely to tell the whole story because records were either not provided, not kept or never made on some aspects of the testing itself.
So what is the possibility that it's contamination? According to the court appointed experts it's unnacceptably high. That doesn't give us a quantifiable number, but we do know that there was the potential for it to occur prior to collection, during collection and during testing. The degree of concern that should be applied is hightened by the fact that even the most basic procedures to prevent it were not followed.
Simply watching the tape showing the collection of the clasp should give a good feel for the "care" with which they treated evidence.
I have no issue with people who geniuely believe that Knox and Sollecito had a part in the murder, but when it comes to scientific evidence it's not a subjective thing. The court selected experts said it had no evidentiary value and to try and twist the findings so that there is a loophole where you can still claim the tests are valid and support your position is absurd IMO. And in this particular case the arguments made are misleading at best or dishonest at worst.
The blog author would be much better advised to simply drop the knife and clasp and return to the supposed "mountain" of other evidence.
My apologies for any incoherencies in the post... It was written in 30 second chunks as time permitted this morning. If you have any questions or if you'd like clarification on anything please feel free to ask.
John
and the Perugia Murder File. Both of them will give a good overview of the guilt side and if you're like me, give you plenty of head scratching moments at the sheer outrageousness of a lot of the positions they stake out.
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