In the famous Greek myth, Princess Ariadne helps Theseus negotiate the Minotaur’s maze by giving him a ball of thread so he could backtrack if he got lost.
The phrase “Ariadne’s Thread” refers to to the problem-solving technique of keeping a meticulous record of each step taken, so that you can always backtrack and try alternatives if your first efforts fail to yield results.
It’s a useful metaphor for understanding the tedious task of challenging DNA evidence. You have to backtrack, note dead ends, attempt iterations that may not yield results, then try again.
It’s a tedious and confusing process. So I’ve written this post to give an overview of how DNA evidence is gathered, the legal procedures available to challenge it, and how “new” scientific DNA evidence is generated.
If you have a loved one convicted on DNA evidence, then this post might serve as a helpful beginning primer. Just keep in mind I’m a post-conviction lawyer, not a DNA expert!
1. Typical DNA evidence at trial.
DNA evidence at trial usually consists of a lab analyst who testifies from a report prepared by the laboratory that employs the analyst. The lab can be either public (there are regional DPS labs) or private. The lab receives a physical specimen, such as swabs or scrapes from clothing that may contain biological material. The lab then uses tools to amplify the DNA material (if there is any) and then gathers and interprets the data by using sophisticated probabilistic genotype programs to develop a DNA profile. This “evidentiary” profile is then compared to a reference profile from the defendant, victim, or any other relevant person.
The lab analyst who testifies doesn’t have to be the analyst who actually did the work at the lab. Anyone from the lab who is qualified can take the case file, review and confirm the conclusions, then come to work and testify about the results. The DNA analyst typically is not involved in the evidence collection process – he or she just interprets the data provided.
Given the above (very rough, non-science expert) summary of how DNA evidence is typically presented, two points come to mind.
First, you can see how the DNA analysis is entirely dependent on the integrity of the original investigation. The DNA lab just gets the stuff and tests it. They don’t find it. They don’t know the logical relevance of the biological material.
Second, when it comes to DNA evidence, the jury and even the lawyers involved in the trial really just see the tip of the iceberg. The reports are just the lab conclusions. The actual data and the “bench notes” taken while the data is being processed usually aren’t admitted during trial or discussed by counsel.
If the DNA evidence is pivotal to the case, it’s common for defense counsel to retain their own expert to review the sponsoring lab’s work. But again, the defendant and lawyers aren’t actually looking at anything other than the reports. This makes sense — lawyers aren’t DNA experts. But you’d be surprised how superficial the questioning of DNA analysts can be during trial. This can even be true when the defense team retains their own DNA expert. Often the defense expert will “verify” the results but not be called as a witness because of concerns that they would just bolster the State’s case.
2. Procedural Pathways to Challenge Original DNA evidence
The Texas Code of Criminal Procedure allows convicted persons to challenge their convictions if they present “scientific evidence . . . that was not available at the time of the convicted person’s trial.” Tex. Code Crim. Proc. art. 11.073 (b)(1)(A). “Not available” means that the methodologies relied upon in the new evidence didn’t exist at the time of trial or have been updated or substantively changed since trial. Article 11.073 is known colloquially as the statute that allows an inmate to file a “junk science” writ. The applicant needs to be prepared to file the 11.073 writ with an affidavit or report from a new DNA expert. He also needs to be prepared to call that witness at an evidentiary hearing. Finally, the applicant will need to make a compelling case that the expert’s conclusions and methodologies could not have been developed during the original trial.
If the convicted person could have developed the scientific evidence during trial but just failed to do so, then he can’t rely on article 11.073. He can probably still plead the evidence as part of a ground for relief, but he’ll have to reframe it as an ineffective assistance of counsel claim under article 11.07. In other words, a convicted person could argue that trial counsel provided deficient performance by failing to fully investigate the case and retain an expert who could have effectively challenged the State’s DNA evidence. By pleading the ground this way, a convicted person would have to meet the normal burden of proof for ineffective assistance, i.e., that counsel was in fact deficient for not getting an expert, and that the error was prejudicial because the undeveloped DNA evidence raises doubts about the integrity of the conviction.
Like with any statutory writ attacking a Texas felony conviction, an applicant has the burden of proof. He has to obtain findings from the trial court, and he has to convince the Court of Criminal Appeals that the trial court’s findings and conclusions are sound and supported by the record. In almost every instance, the applicant should expect the State to vet the proffered DNA evidence with their own expert.
3. How New Scientific DNA Evidence is Developed.
Let’s say you have a family member who is convicted for a serious crime and that that DNA evidence was part of the State’s case. So now what? How do you get new scientific DNA evidence or try to challenge the original conclusions by means of the procedures outlined above?
There’s a couple of ways.
First, you can file a Chapter 64 motion to retest DNA from a collected piece of evidence or collected sample. I won’t get into the nuts and bolts of Chapter 64 motions in this blog post. But you can see that with this strategy you are going back to the “root” of the DNA evidence, the logic being that maybe the piece of evidence contains the DNA of another person. Or maybe a piece of evidence wasn’t tested but should have been. Or maybe there is another method of extraction that can be used to remove or isolate biological material.
Here’s two examples:
- During the original investigation, a stain from a pair of jeans was collected and tested, but now you want to test another stain from the back of the jeans that was never collected;
- swabs from the handle and trigger of a gun used in the murder were collected and tested, but now you want to swab the muzzle and submit that to a lab for further testing;
I can tell you from experience that both of those requests would face serious procedural hurdles with a filed Chapter 64 motion for further testing, but you get the general idea.
Second, you can challenge the lab work and analysis. Under this strategy, you would typically hire a DNA expert would would check the lab’s homework, both on the methodologies used to extract and amplify the DNA and the conclusions regarding the deduced profile. With this strategy, you are making sure the data and LR’s (likelihood ratios) are correct.
With older cases, you start to run into problems such as “allele drop out” (DNA samples degrade over time), and also stale data. The field of DNA analysis has improved drastically over the last few decades, and many older data sets can’t be assessed with modern software programs such as STRmix. So with older cases you are often arguing over interpretations of data using dated methodologies.
With the second method, the “new” evidence ends up being a second expert opinion or report that contradicts earlier conclusions.
4. The only way to Challenge DNA Evidence is to Follow the Thread
DNA cases worth challenging will be complicated. “Good” DNA evidence can grow stale. The math gets muddy, especially when you have multiple DNA sources and mixtures of contributors.
When faced with such evidence, it’s tempting to hope there is a silver bullet, a single flaw that, when found, will kill the State’s case. Unfortunately, any analysis used to undermine the State’s DNA evidence will itself be subject to qualification and challenge. It’s easy to get frustrated with the process.
But don’t forget Ariadne’s ball of thread! Essentially, that’s what the State gives you. Each set of data, each report, and each analyst involved creates a carefully recorded trail. What you have to do is work slowly backwards, checking each step as you go, looking for flaws. Sometimes you have to go all the way back to the beginning of the maze.
So . . . be methodical and don’t give up!
As always, this is a general information post and not legal advice. Please find a good post-conviction attorney to advise you on your particular case.