While the creators of Making a Murderer did a spectacular job of making the Steven Avery case easy to understand, sometimes things can still get a little lost in translation – specifically, the DNA evidence where Avery’s blood was found all over Halbach’s car as well as her DNA on the bullet found in his garage. I like to consider myself an intelligent person and hell, I still got a little lost with all the EDTA detection jargon shit being thrown around.

Well never fear folks, since a fancy-pants scientist is here to explain all those big- words that you can’t even find in the dictionary to us peasants. However, we do need to put a DISCLAIMER here, which is that while this guy says he’s a scientist and certainly sounds like one, we couldn’t verify his occupation. At the same time though he does have blog posts dating back as far as 2012 in which he talks about his job at a clinical lab, and the chances that he faked them are likely slim. Not like he knew we were gonna pick up his post, right? So without further adieu, here’s what Probable-Scientist Chad Steele had to say about the blood evidence used in the Steven Avery trial:

I have recently watched the documentary series, “Making a Murderer.” I know that everyone has thoughts and opinions after watching this, and I am no different. However, I would just like to share some facts about a few pieces of evidence, and the fault in how they were used. My current profession revolves around making sure scientific tests measure exactly what they are supposed to measure and do so in a consistent, reliable way. It is in this spirit, that I feel like I am allowed to weigh in on the “DNA bullet” and the EDTA detection.

When these tests are developed, there are controls put into place that ensure the test was run correctly. These controls are usually of a positive and negative variety: the positive control will have a known substance or quantity that will produce a result that falls within a specific range and the negative control will produce no result (a zero, nothing detected, etc.). In order to be able to produce results that can be labeled “scientifically valid,” the test must contain controls. If something comes up in the negative control, it is an invalid test. If the positive control produces a result that is abnormal or out of range, it is an invalid test. An invalid test means, in effect, that there are NO ACTUAL TEST RESULTS. In regards to whatever sample you were testing, in that specific test, there are no results. This prevents reporting of tainted, skewed, and erroneous results.

While DNA testing the bullet, the technician performing the test found that some of her own DNA got into the negative control. Because the negative control was no longer negative, it was an invalid test. Because she used the entire sample, she decided to submit a deviation, so the results from the sample could be used despite an invalid test. This is extremely poor science at best, and at worst…well, planting evidence and bias doesn’t need to be mentioned any more than it already has. Even mentioning that the bullet had the victim’s DNA on it is a lie. It was based on an invalid test. Scientists NEVER draw conclusions from an invalid test. The fact that she did not save any sample to be tested again is not the defendant’s fault. It is an error. This situation should have been deemed “inconclusive” or “no test” and, thus, there is no test result that became evidence.

Detecting EDTA from a blood swab sample sounds fairly straightforward. However, without having a documented limit of detection, no scientist can accept what the test can and can’t do. If one does not know what a test can and cannot do, he or she cannot use that test to draw any conclusions. Let’s discuss the “limit of detection.” Imagine one particle of flu virus lands on your arm. There is no person in their right mind that would knowingly be able to feel it land on his or her arm. On the other hand, everyone would be able to feel a brick land on their arm. There is a “limit of detection” that the human sense of touch inherently has.

In regards to the documentary, the test showed that no EDTA was detectable in the blood swabs. Without a limit of detection, this information means nothing, absolutely nothing. It is possible that the test could only detect EDTA if EDTA composed at least 50% of the sample. The amount of EDTA in blood tubes is miniscule, almost negligible compared to the amount of blood. We are talking about 7 milligrams of EDTA in a 4-mL blood tube. If 0.1 mL was taken out, it would, at most, contain 0.2 mg of EDTA. The blood was swabbed from the vehicle, and probably only 1/10 of the blood (0.01 mL of actual blood), thereby diluting it further. The swab used was also wetted with some sort of solvent, maybe 0.1 mL. Now, there’s only 0.002 mg of EDTA in the blood swab. The swab most likely was diluted further for test purposes, probably taking the swab and re-suspending into at least 1 mL of solution. Using my numbers, which are probably conservative, the test would have to be able to detect 0.0002 mg (0.2 µg) of EDTA in 1 mL of sample. Outside of the amount of EDTA present in a 4-mL blood tube, these numbers are hypothetical for illustrative purposes only.

The testing that would have been required to scientifically validate this test would have required some time. After following standard validation procedures, I would have taken blood from an EDTA vial (any blood) and put it onto a vehicle surface. After the blood was completely dry, I would have used the same blood swabbing and collection procedure used during the investigation, and then tested that sample. This would be a positive control, since the technician would know that there was EDTA in that sample. Does the newly-developed test detect the EDTA? If so, repeat it at least 10 times, and you have a strong scientific ground to make the statement that there was no EDTA present in the blood from the vehicle. If the test does not detect EDTA from the experiment above, one cannot make any mention about the presence or absence of EDTA in the blood swabs from the vehicle because the test could not detect EDTA amounts that small.

I do not know all of the work that went into developing the EDTA detection test. However, using the results and drawing a conclusion based on those results, without having a well-defined test with a limit of detection, is a LIE. I will not mention using the results from only 3 swabs to extrapolate results onto the untested swabs. That was just plain unethical, and I am glad a rebuttal witness for the defense made that clear.

I have plenty of opinions about what I saw in the documentary, which I may share later. I just wanted to lay out some facts from the scientific field about what I saw. Based on what I have presented here, pretend the bullet had no trace of the victim, and pretend the blood swabs were never tested for the presence of EDTA. That is what should have been done.