DNA evidence in the Hank Skinner case

[Chris_Halkides]

Hank Skinner has just been granted a stay of execution for the 1993 murders of his girlfriend Twila Busby and two adult sons. He and his attorneys wish to test items such as fingernail scrapings from his girlfriend, the rape kit, the windbreaker jacket, and the murder weapon. It is pertinent to the discussion of mitochondrial DNA testing that another plausible suspect is Ms. Busby's maternal uncle, Robert Donnell, now deceased. Some background reading can be found in a series of articles by the Skeptical Juror, and two articles by Radley Balko.

Some mitochondrial DNA testing was performed on the hairs in Ms. Busby's palm. William Shields provided an affidavit. Dr. Shields, wrote, “If we put all of this together, there is direct evidence that the 011D-2 hair found in the victim’s hand did not come from either her or Mr. Skinner.”

I would like some thoughts on this report. One question that occurs to me is whether or not Mr. Donnell is excluded with respect to 011D-2. In addition, I seek opinions on what further testing would be useful on either the hairs or the other items. It is not my intention to discuss Mr. Skinner's or Mr. Donnell's factual innocence or guilt, except to the degree that the DNA forensics implies.

 

[Lowpro]

If they are found not to be Hank's hair through DNA, then it means that it's not Hank's hair in Ms. Busby's hands... that's all.

There's more evidence in this trial than just DNA.

 

[Chris_Halkides]

If they are found not to be Hank's hair through DNA, then it means that it's not Hank's hair in Ms. Busby's hands... that's all.

There's more evidence in this trial than just DNA.

Lowpro,

I can see the rationale of discussing the other forensic (medical) evidence in this thread, but I am trying to avoid a general discussion of the case, which would be out of place in a science and medicine discussion area.

 

[Lowpro]

Okay, well let me ask you this. What more do you think DNA evidence provides than DNA evidence?

Its total significance is that the tissue found on the victim may match or may not match Hank's DNA. That is its significance. Now, you can infer that if it's not his DNA and someone else, then someone else was within hair-snatching distance of the deceased. That's only an inference, not data. And inferences aren't allowed by your declaration, so I guess I cannot talk about that and only remind you that...

If they are found not to be Hank's hair through DNA, then it means that it's not Hank's hair in Ms. Busby's hands... that's all.

Anyways I read your comments in regards to the affidavit. First off, Donnell is dead, and it's harder to get DNA I imagine; it takes a bit of time at the least and that's assuming there's DNA to get (if he's cremated it's almost certainly out of the question) but the first step is to test Hank's DNA to see if it matches; again it doesn't exonerate him but I definitely think it'll call his Capital Punishment sentence into question considering the current trend of DNA analysis and burden of proof.

 

[Chris_Halkides]

Okay, well let me ask you this. What more do you think DNA evidence provides than DNA evidence?

Its total significance is that the tissue found on the victim may match or may not match Hank's DNA. That is its significance. Now, you can infer that if it's not his DNA and someone else, then someone else was within hair-snatching distance of the deceased. That's only an inference, not data. And inferences aren't allowed by your declaration, so I guess I cannot talk about that and only remind you that...

Lowpro,

I would say that mitochondrial DNA testing is more prone to contamination than regular STR profiling, so I am wondering about the frequency with which this might be expected to happen. I would like someone to comment on my tentative conclusion that any mitochondrial DNA sample for which Ms. Busby is excluded also excludes Mr. Donnell.

I also found some of Dr. Shields' comments a little worrisome; he did not seem to think that Orchid Cellmark had correctly interpreted some of the data, although he also noted that he only had access to the paper copies of the electropherograms, not the (raw) electronic data files. I also wondered whether or not they attempted plain-vanilla STR typing first.

With respect to your first question, I did not intend to exclude inferences from the forensic data. Perhaps I could have worded my opening comment differently; I was trying to stay within what I thought a S&T forum would want. I agree to the general proposition that the mere existence of DNA does not by itself tell you when or how it arrived on an item of evidence. However, its location (intimate versus non-intimate areas of the body) might be helpful in distinguishing innocent from inculpatory deposition.

 

[Robrob]

Well, if nothing else - if the DNA turns up to be Hank's it pretty much seals his fate and prevents endless rounds of "was he innocent or not?"

 

[Chris_Halkides]

Was GeneScreen's analysis entirely objective?

Let me quote from a pro-Skinner site:

"One would have to wonder why John Mann would choose a private lab to do the testing at $8000-$12000 cost to county taxpayers when he could have gotten the state's DPS lab to do it for free. The answer lies with GeneScreen's MT DNA analyst William "Bill" Watson. Houston/Harris County Capital Crimes Division Assistant District Attorney Kelly Siegler had a fondness for Watson and used him in most of her death penalty prosecutions because Watson was well known for giving prosecutors the results they wanted. Just as panhandle pathologist Ralph Erdmann M.E. gave Lubbock D.A. Travis Ware "made to order" autopsy results, maybe Bill Watson gave John Mann "made to order DNA test results"? This could explain why the news stories quoted Mann as saying he "expects" certain results. Indeed, maybe the fix was in, Mann expected GeneScreen to deliver (pseudo) inculpatory test results against Hank? The truth is, none of the tested hairs 'clutched' in the victim's hands belonged to Hank Skinner but instead to an unknown third party! Once the Court forced GeneScreen to turn over to the defense all hardcopy data related to their testing and once that data was examined by a competent, neutral analyst, GeneScreen's "misinterpretations" became glaringly apparent. Based on this evidence, Hank's attorneys have once again renewed their motion for discovery to DNA Test the six items of evidence listed at the beginning of this section."

MT is short for mitochondrial. GeneScreen later became Orchid Cellmark, IIRC. Do people here think that the above interpretation is correct? Reading between the lines of Dr. Shields' deposition, I see some support for the view above. I also agree very strongly with Dr. Shields' comments to the effect that until one examines the underlying electronic data files, one's analysis is not complete.

 

[Robrob]

Just as panhandle pathologist Ralph Erdmann M.E. gave Lubbock D.A. Travis Ware "made to order" autopsy results, maybe Bill Watson gave John Mann "made to order DNA test results"? This could explain why the news stories quoted Mann as saying he "expects" certain results. Indeed, maybe the fix was in, Mann expected GeneScreen to deliver (pseudo) inculpatory test results against Hank?

Sounds like they are already covering their bases for an anticipatory "the test was rigged!" defense.

The truth is, none of the tested hairs 'clutched' in the victim's hands belonged to Hank Skinner but instead to an unknown third party!

As previously mentioned, the hairs not being Hank's means nothing at all in regards to his guilt or innocence. The only meaningful result would be if the hairs were determined to be Hank's.

 

[Lowpro]

I'll be honest I cannot motivate myself enough to research the motivations on this issue. I am disturbed at the accusation of a lab that would provide "made to order" results though... but I cannot provide any insight into their decision. There's far more mtDNA than nDNA so there's no conspiracy on why they'd use it, especially in hair samples which may be old or degraded.

It sounds like this thread, if we are to continue the political motivations, may not belong in the Science forum =\

Now, if the hairs do NOT match Hank we are back to the fact that all it means is the hairs in her hand do not match Hank. There's more evidence than just the hairs that put Hank on Death Row (I would assume, but there's more to a trial than just evidence...sadly)

 

[Chris_Halkides]

problematic forensics

I'll be honest I cannot motivate myself enough to research the motivations on this issue. I am disturbed at the accusation of a lab that would provide "made to order" results though... but I cannot provide any insight into their decision. There's far more mtDNA than nDNA so there's no conspiracy on why they'd use it, especially in hair samples which may be old or degraded.

It sounds like this thread, if we are to continue the political motivations, may not belong in the Science forum =\

Now, if the hairs do NOT match Hank we are back to the fact that all it means is the hairs in her hand do not match Hank. There's more evidence than just the hairs that put Hank on Death Row (I would assume, but there's more to a trial than just evidence...sadly)

Lowpro,

DNA technicians sometimes fake negative controls and are sometimes told too much information about a case. See William C. Thompson's article, "Tarnish on the Gold Standard," for a good introduction to this topic. Here is a link on mtDNA that I have not yet had time to study.

I will try to start a thread in another subforum this weekend for the nonforensic aspects of this case.

 

[Chris_Halkides]

hair

Sounds like they are already covering their bases for an anticipatory "the test was rigged!" defense.


As previously mentioned, the hairs not being Hank's means nothing at all in regards to his guilt or innocence. The only meaningful result would be if the hairs were determined to be Hank's.

Robrob,

I think that the identity of the person or persons whose hairs were found in her hand are probative (but would fall short of definitive proof) either way (whether they are Hank's or someone else's hairs). Can you expand on your reasoning on why you came to a different conclusion?