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By Megan Cooley

Megan CooleyPerhaps over the holiday break you binge watched the Netflix documentary Making a Murderer like I and a few thousand other people. There are several different online chat forums filled with fans of the show poring over the evidence that was put forth to convict Steven Avery in the murder of Teresa Halbach.

For those who have not seen this documentary, it’s intriguing from a few different aspects. Steven Avery was first convicted of rape and sexual assault of a woman back in the late 1980s. After spending 18 years behind bars, DNA evidence exonerated him and he was released from prison. This was one of the first times DNA evidence had been used to overturn a wrongful conviction. DNA evidence is the most conclusive type of physical evidence that can be brought against somebody. DNA can be extracted from bodily fluids found on victims or from other pieces of evidence at the crime scene and be matched with a suspect’s DNA. Misidentification by DNA analysis is less likely than a person’s odds of winning the recent $1 billion lottery; however, samples can become contaminated during analysis and diminish the accuracy. Avery brought a lawsuit against the Manatowic, Wis., sheriff’s department for his wrongful conviction. As the trial was winding down and it appeared that Avery would be awarded a financial settlement, Halbach vanished. Within the next two weeks, Avery would find himself behind bars once again, this time convicted of murder.


Besides the twisted plot line, the evidence presented during Avery’s trial was equally troubling. Nothing seemed to add up. Key pieces of evidence were not found until Avery’s house had been searched several times, and even after several searches, no blood or DNA belonging to Halbach was ever found. The only place where her blood and his blood were together was her vehicle. The defense suggested that this blood was taken from a tube of blood previously taken from Avery, which was in possession of the sheriff’s office since his first trial. In other words, the defense was suggesting the sheriff’s department was framing Avery for Halbach’s murder. The defense planned to prove this by showing that the blood shown to be that of Avery’s in the car contained the anticoagulant used to preserve blood, EDTA.

This is not the first time that this tactic had been used in a trial. O.J. Simpson’s defense lawyers also wanted to analyze for EDTA blood found at the crime scene. The evidence was received similarly in both Simpson’s and Avery’s trials. The Simpson prosecution’s witness showed there was no EDTA in the blood found at the scene, and the defense witness argued that nothing can be taken away from the evidence shown.

I found what I am assuming is the FBI’s original published work for a method that would allow them to analyze EDTA in blood samples. The method development was routine: they established a dynamic range and showed it was linear and had application toward biological matrices. The method does lay out pitfalls, such as reproducibility issues due in part to no internal standard being used, and they also pointed out that there are a lot of sources for EDTA, e.g., in foods.

What they don’t show is the stability of EDTA in samples over a period of time. When the defense witness in the Avery trial argued against the prosecution witness, she stated that proper controls were not run for the samples in evidence and so it was hard to establish whether the EDTA level found in the blood in the car (which was none) was actually nothing or was simply, as she put it, below the detection limit for the method, likely due to sample pretreatment. From what I have seen in various searches, no one has really established the stability of EDTA in blood samples over time. It is well established that blood samples need to be stored at 4°C or degradation will occur. To really consider this as conclusive evidence, these parameters must be established. This, like most things, was another crushing blow for the defense. Avery is currently serving a life sentence for this crime.

Does the evidence in your opinion suggest that he did it? How do you perceive the blood evidence put forward in the trial? How would you propose to handle the analysis so this type of evidence could be reliable in court?

Megan Cooley is not authorized to speak on behalf of MRIGlobal, and the opinions expressed are my personal opinions and not those of MRIGlobal.

Megan Cooley, Ph.D., is a postdoctoral fellow at the University of Kansas Medical Center. Her research is focused on understanding the effects of the tumor microenvironment on acquired chemoresistance and metastasis.