The use of DNA evidence as a tool to implicate people accused of crimes must rank as one of the most momentous advances in criminal justice technology since the development of fingerprint evidence in the early 20th century. The ability of a prosecuting attorney to tell a jury that, based on a tiny sample of biological evidence found at a crime scene, the accused can be identified to odds of millions to one as the person who left it there seems daunting if not damning. You could be excused for thinking that unless you can assemble the same “Dream Team“ of high-priced celebrity lawyers that successfully defended O.J. Simpson against murder charges in the early 1990s, the best you can hope for when confronted with the use of DNA evidence against you is to cop the best plea bargain that you can instead of facing a “slam dunk“ case by the district attorney.
But is that always true? Is the modern use of this kind of genetic technology really the kind of ultimate evidentiary weapon that television crime dramas can make it out to be, or that police and prosecutors would like you to believe it is? Are there any ways that you can challenge the use of DNA evidence being used against you in plea negotiations or at trial?
Actually, a number of methods and tactics do exist to plant that kernel of “reasonable doubt“ into the minds of at least some of the jurors when it comes to DNA evidence, and in criminal cases the prosecution must overcome any reasonable doubt of guilt to secure a conviction. The ones we will discuss below are just a few that a capable defense attorney can use on your behalf.
Making DNA technology—and its potential problems—understandable to the jury
It has been said that any technology, if it is sufficiently advanced enough to those seeing it in use, will appear to be magic. DNA evidence is a good example of how this can happen. Most people cannot even say what “DNA“ stands for, not to mention how it works as evidence. Prosecutors count on this seemingly magical complexity to awe jurors into a mind-numbing sense that it is infallible. A good defense attorney knows that his first challenge is to strip away this illusion, and that begins with educating the jury so that they are no longer mentally intimidated by the science involved. This often takes time, the use of expert witnesses and a careful approach to explaining how human errors can make even the most advanced technology unreliable, but the effort is worth it if at least one juror can start to think critically instead of reflexively about the possibilities.
Forcing the prosecution to prove it got everything right
Sometimes planting the seed of reasonable doubt doesn’t require attacking the technology as much as revealing possible mistakes made by those who are relying on it. A single slip made in handling the biological sample from which the DNA was taken (“chain of custody“ errors) can open the door to doubts about who the sample came from, or where it came from.
Showing potential weaknesses in the training of the personnel working in the lab that performed the sample analysis or the procedures they used can also create misgivings in the minds of jurors about the accuracy of the lab work. Remember, it is the responsibility of the prosecution to prove that it did everything correctly, and the more complicated the technology and the processes involved, the more likely it becomes that somewhere along the line somebody did something incorrectly.
Defending against DNA evidence requires a comprehensive approach
Although DNA evidence is not automatically a sure thing when used against you, you should not underestimate its potential to sway a jury. From the opening statement through examining and cross-examining expert witnesses and thoroughly investigating the chain of custody of the DNA sample by the police and the test laboratory, your defense attorney will need to be systematic in raising plausible doubts about how the evidence was obtained, whether it was subject to contamination, and what it really means in terms of the prosecution’s case. Because of this need for attention to detail throughout the trial, you should choose defense lawyers who are already knowledgeable about DNA evidence and experienced in representing clients against whom it has been used.