Your DNA Goes Where You Do Not

Use these links to jump to different sections:

• DNA Linkage Does Not Equal Guilt
• DNA Sources Beyond the Crime Scene
• DNA Exoneration

Watching criminal procedurals on TV, you’ve no doubt learned that your genetic fingerprint is embedded in your DNA, and that you leave this telltale stuff behind you in traces of your skin, saliva, and sweat.

As such, with the rise of DNA forensic testing, DNA databases, and genetic testing services from companies like 23andMe, you might think that linking suspects to airtight criminal convictions (or exonerations) through their DNA profile has become a straightforward process.

However, you’d be wrong.

DNA Linkage Does Not Equal Guilt

Criminal defense attorney Kush Arora regularly faces this public misconception. “There’s an assumption much of the time,” he says, “whether it’s on the part of a judge or a jury, that if there’s DNA, that DNA must be correct. It can be frustrating.”

In other words, just because a DNA sample from the crime scene matches that of a particular suspect, it doesn’t mean the reason is because of that individual’s guilt.

There are actually many aspects to the collection, processing, and analysis of DNA testing that can raise questions about the certainty of such a conclusion.

“We’ve had cases thrown out for issues with DNA where there’s a match,” says Arora,” but the manner in which the evidence was collected or stored was faulty, or there’s an issue with the chain of custody—any number of things that could call into question the validity of the results.”

DNA Sources Beyond the Crime Scene

In addition, a little-understood facet of DNA science has to do with how DNA information can travel, landing on an object that the source never had contact with.

This type of DNA transfer was behind the so-called Phantom of Heilbronn, a suspected serial killer with a trail of more than 40 crimes throughout Germany, France and Austria. The DNA trail led to a factory worker who produced the swabs used to collect law enforcement DNA samples. She was never at a crime scene herself, but she had contaminated the swabs before they ever left the factory.

Our DNA and genetic material is everywhere, and it can travel without us. One study found that as much as 75 percent of crime scene materials contained transfer DNA, sometimes carried from one location to the next. Another found that one in five people have someone else’s DNA and genetic information under their fingernails at any given time.

DNA Exoneration

It was this last circumstance that nearly landed Lukis Anderson on death row for a Santa Clara County murder he didn’t commit. His DNA was found at the crime scene, under the fingernails of the victim. Fortunately for Anderson, records from a nearby hospital gave him a documented alibi: He had been admitted to health care at the time the crime occurred. The mystery of his itinerant DNA could best be understood by speculating that the same paramedics who had treated Anderson earlier that day had also responded to the 911 call at the murder scene.

Where DNA transfer is concerned, as with the Anderson case, much remains to be understood about how transfers occur, and what impact this has on the conclusiveness of DNA evidence found at a crime scene. For now, it seems that confirmation bias can be a substantial hurdle for juries to overcome, as Arora attests.

If you have a question about how DNA or genetic data may be utilized in a case you’re involved with, contact an experienced Oregon criminal defense attorney to make sure the matter is properly handled. 

For more information on this area of law, see our overview of criminal defense.