The Subjectivity of DNA Analysis

I can only imagine the sinking pit in your stomach after being falsely accused of child abuse based on DNA analysis.

You know you've done nothing wrong but feel like this manner of evidence is insurmountable. After all, you've always been led to believe that DNA is virtually irrefutable.

Well, that’s not really the case. All is not what it appears to be in the world of forensic science. Sure, in television shows and movies, it might seem like you can't disprove the validity of DNA. But we live in the real world.

DNA is nowhere near as objective or infallible as you might fear.

Knowing this fact can pay huge dividends in getting your name off the Child Abuse Central Index. Through the information discussed here, you'll see how DNA evidence being used against you can be overcome and proven questionable.

It seems odd to consider that science, which is based on being purely objective, could hold some form of bias. The results of DNA analysis, for instance, should be cut and dry.

Now, it's not necessarily the science itself that's subjective or biased in any way. But forensic scientists, for instance, are people. No matter how much they try to make the various mechanisms involved unbiased, humans are always susceptible to their nature.

The issue is complicated, but in any given legal scenario, DNA must be interpreted by these people. While they might not have a vested interest in the emotional stakes of this situation, they are aware of the alleged course of events and the context involved.

Through this lens, it's theorized in a scholarly article called "Subjectivity and bias in forensic DNA mixture interpretation," that this kind of evidence isn't always as impartial as it seems. (I.E. Dror, G. Hampikian, Subjectivity and bias in forensic DNA mixture interpretation, Science and Justice 51 (2011) 204-208.)

In the article mentioned above, the notion that DNA is the gold-standard for objectivity is put in its proper place. The media, technical literature, and the legal system, for example, have all perpetuated this myth.

Not all DNA data is cut and dry. Yes, in certain circumstances, it is very reliable and basically immune to various challenges. When DNA mixes (meaning there is DNA from multiple people together in one sample) and interpretations of the evidence must be made by the DNA expert, DNA evidence suddenly falls to the whims of subjectivity and bias.

The research performed that was presented in the article mentioned above examined how 17 separate North American DNA analysts had to interpret the same criminal case, yet provided inconsistent interpretations.

Plus, the lab had a pre-trial conclusion that most of the subjects disagreed with, believing that context unrelated to the case, and not coming directly from the evidence, influenced the DNA analyses.

The study looked at a sexual assault case with multiple potential offenders who were all ruled guilty.

A cooperative assailant testified against several other individuals. The analyst claimed the DNA results couldn't exclude those individuals from being contributors to the mixture. It was through this corroboration that the guilty verdict was reached.

Later, when, as part of the research, the evidence was presented to the test group without explaining the context in the paragraph immediately above, 12 out of the 17 examiners ruled that the sample could actually exclude the suspects in question. Only 3 of the analysts thought that they could not be excluded, while 4 deemed it inconclusive.

Consider that out of this group, only 3 of the analysts said they couldn't exclude, which is the lowest number. Combine that with an inconclusive classification meaning the cooperating assailant's testimony would likely not be allowed. Suddenly, you get a sense of injustice.

The disparity between results shows the lack of subjectivity in these kinds of samples. If the same evidence gives these many different answers, how much of a gold standard can it really be?

I discussed earlier how more straightforward samples remove most – if not all – interpretation and context from the table.

Alternatively, mixed DNA is more commonly ambiguous and complicated to interpret. There's a quote from the Forensic Science Society's work, saying, "if you ask 10 different analysts, you'll get 10 different answers." It tells you everything you need to know.

When your accusers use DNA to incriminate you, you'll find that the evidence's quality is integral. If you’re dealing with a mixed sample, you can ask questions that assess how this DNA is being interpreted.

There will be times when it's challenging to discredit DNA evidence, but that doesn’t mean all hope is lost. There are other ways to poke holes in the government’s evidence.