The Air We Breathe: DNA, Privacy, and the Future of Forensics

Imagine taking a stroll in your local park, leaving invisible traces of yourself behind with every breath you take, every cup of coffee you sip, and every surface you touch. Now, picture a world where these minute genetic breadcrumbs can be collected, sequenced, and used to learn intimate details about you. This is not a dystopian future. This is now.

In her New York Times report on environmental DNA and genetic privacy, Elizabeth Anne Brown describes research by University of Florida scientist David Duffy and his colleagues. Their work showed that human DNA could be recovered from water, sand, and air, raising privacy concerns about a method already used to study wildlife.

Previously, the focus of eDNA was primarily on wildlife conservation, detecting invasive species, tracking vulnerable wildlife populations, and even rediscovering species thought to be extinct. But as Brown’s article explains, this technology is not limited to animal DNA. It’s capable of extracting human DNA from the air we breathe and the water we touch. It can gather medical and ancestry information from these trace amounts of DNA, which raises significant privacy concerns. Additionally, the implications of eDNA technology for law enforcement are profound and potentially transformative, but they also raise significant legal and ethical questions.

Law enforcement has a longstanding relationship with DNA. Since the introduction of forensic DNA testing, DNA evidence has played a pivotal role in solving countless crimes. It has also been instrumental in exonerating individuals wrongly accused or convicted. However, the potential to gather DNA from environmental sources presents a whole new landscape for law enforcement.

The FBI’s Combined DNA Index System, or CODIS, lets participating laboratories compare DNA profiles using selected genetic markers. Recovering human DNA from the environment does not automatically produce a profile suitable for CODIS. A sample’s usefulness depends on its quality, the markers recovered, and whether DNA from different people can be reliably distinguished.

Environmental DNA could help investigators develop leads, but its collection and analysis raise Fourth Amendment questions. The Fourth Amendment protects against unreasonable searches and seizures; whether police need a warrant depends on the circumstances and any applicable exception. If police obtain DNA evidence in violation of a defendant’s constitutional rights, the defense may seek to exclude it through a motion to suppress.

Police may argue that a person has no reasonable expectation of privacy in genetic material left behind in public. That argument should not be treated as blanket permission to collect and analyze human DNA from air or water. The place and method of collection, the scope of testing, and the governing law all matter.

Environmental samples can contain degraded DNA and genetic material from several people. Those features can complicate efforts to identify whose DNA is present. The reliability of a result depends on the collection method, laboratory controls, sequencing technology, and interpretation. Recovering a person’s DNA also does not, by itself, establish when or how it entered the environment.

The use of new DNA collection techniques, like eDNA, is understandably enticing for law enforcement, as it may provide new avenues to solve crimes and bring justice. However, the potential for misuse or overreach is substantial. As we’ve seen with other forensic techniques, such as blood spatter analysis and bite mark evidence, the adoption of new methods without robust validation and regulation can lead to wrongful convictions.

Similar concerns about treating preliminary results as proof arise with field drug tests and wrongful convictions, where a positive screening result can be mistaken for a confirmed finding.

In this “wild west” of DNA technology, as described by Erin Murphy, a law professor at the New York University School of Law, it’s essential to establish clear guidelines and regulations for the use of eDNA in criminal investigations. This should include establishing protocols for collection and analysis, safeguards against misuse, and mechanisms for challenging the use and admissibility of eDNA evidence in court.

In a Florida criminal case, expert testimony about eDNA must meet section 90.702’s requirements for reliable expert evidence. The defense can challenge whether the opinion rests on enough facts or data, uses reliable methods, and applies those methods reliably to the case.

Moreover, there’s a need for more extensive research into the fundamentals of eDNA, like how it travels through air or water and how it degrades over time. As the science behind eDNA matures and becomes more understood, it’s critical that legal understanding and regulation keep pace.

While eDNA may provide law enforcement with a powerful new tool, it’s vital to balance the potential benefits with the protection of civil liberties. As we venture into this new frontier, we must ensure that the pursuit of justice does not come at the expense of individual privacy and civil rights.