Flawed DNA Evidence In The Steven Avery Case

Flawed DNA Evidence In The Steven Avery Case

Flawed DNA Evidence In The Steven Avery Case

Redditor /u/pap3rw8 is a biologist who works with blood and DNA on a daily basis. Below is their perspective about the flawed DNA evidence in the Steven Avery Case in which they posted to Reddit.

The DNA evidence in the case was very minimal and also very, very contaminated and some of it was contaminated by the ‘forensic expert‘ Sherry Culhane. I don’t understand how this ‘evidence’ was even admissible in the first place. Again, this is one of the many issues that went wrong with this case and this is why both Steven Avery and Brendan Dassey need new trials at the very least- in reality, they need to be released and the real murderer needs to be brought to justice.

Here is /u/pap3rw8‘s take on the DNA evidence:

Sorry for the long post. TL;DR I have serious doubts about the integrity of the DNA tests based on the procedure that the expert described. She didn’t take enough precautions against contamination and even petitioned to have proven contamination disregarded. It’s just sloppy science, plain and simple.

I am a biologist employed in a genetics research lab at a major institution, so I work with DNA and blood on a daily basis. Among other procedures, I regularly perform DNA extraction from blood and DNA amplification (PCR); both of which are involved in forensic genetics. I see big problems with the procedure that the “expert” described. She made some significant errors and didn’t take enough precautions to reduce the potential for cross-contamination. I have based this primarily on what appeared in the show; I’m going to go through the transcripts soon and see if there’s anything more there. I think the problems I noticed should have been enough to discredit at least some of the DNA evidence, if not all of it.

Please reply if you want more details or have any questions / insights. I would love to hear from other users who have experience in this field.

The contamination problem:

— Just so you know, the amount of DNA needed to contaminate a sample is incredibly small; the amplification process is exponential so a microscopic fleck of DNA can ruin your whole PCR run. This is especially true if there isn’t much DNA (or none at all) in the sample to begin with, since the contaminant could out-pace the less-concentrated intended target during amplification.

— In my lab, if ANY contamination shows up in the controls, the whole batch is necessarily deemed contaminated and must be discarded. Contamination happens. You do whatever you can to minimize the risk, but you can’t expect it to go away and you certainly can’t ignore it. I think it’s appalling that she was allowed to use a deviation-from-protocol waiver to gloss over the problems with the bullet test.

— If I were ever working on a genetic test on which a man’s life hung in the balance, I would take extra precautions against contamination that the expert did not. First off, she said that she was working on an open lab bench with plenty of other potential DNA sources close by. This is asking for trouble. I would perform a test this critical in a freshly-cleaned sterile containment hood to reduce the chance of any stray DNA getting in the samples. I would use unopened aliquots of the necessary reagents, change my gloves regularly, and have someone watching me to check my work.

— She said that she was distracted during the procedure and was instructing some new technicians. This was definitely not the appropriate time to do a demonstration. Distraction could lead to any number of possible minor oversights on her part that lead to cross-contamination. Maybe she didn’t change her gloves when necessary, maybe she forgot to switch pipet tips between samples, maybe she was moving things around too much to show the new techs, etc. There was even some speculation that she was drunk on the job, which could cause all kinds of sloppiness.

I also have serious concerns about some other science presented in the trial, most obviously the EDTA test. I don’t trust the FBI’s testing procedure AT ALL. Without providing the minimum detection level of their test, any negative result is completely meaningless. I was going to write more about this, but /u/Arseovrteakettl[1] just posted an excellent review of why the test is bullshit. I encourage you to read his post. https://www.reddit.com/r/MakingaMurderer/comments/43olbt/a_clarification_about_the_edta_test/[2] 

Update: I learned a little more about the EDTA test, still not very confident in it. See my reply below.[3] 

Edit: If anyone knows which portions of the transcript (or other documents) deal with DNA, can you point me to them? That would save me a bunch of time searching through hundreds of pages.


What are your thoughts on pap3rw8‘s post?

Sherry Culhane should be ashamed of herself for the way she handled the DNA in this case. How does still have a job?

What are your thoughts on the DNA evidence that was presented at the trial? Do you think the DNA ‘evidence’ should have been admissible?

I believe there was flawed DNA evidence in the Steven Avery case and that is what was one of the things that got him convicted – if it wasn’t for the DNA ‘evidence’, they wouldn’t have much more evidence to get a conviction – so they had to do whatever they could to get SA’s DNA onto whatever evidence they needed to show he was linked to the murder of Teresa Halbach.

Check out my other posts about the different theories about this case and whether or not Steven Avery and Brendan Dassey are innocent or guilty. There are a lot of posts about this subject on my blog, so you’ll have a good amount of reading for awhile!


I’ve been doing podcasts, go and check them out over at iTunes, Google Play and Stitcher!



Flawed DNA Evidence In The Steven Avery Case
Flawed DNA Evidence In The Steven Avery Case
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