Every two minutes, we shed enough skin cells to cover nearly an entire football field. With a single sneeze, we can spew 3,000 cell-containing droplets into the world. And, on average, we leave behind between 40 and 100 hairs per day. As long as we live in the world and leave our homes each day, we can’t avoid leaving a trail of our DNA in our wake.

Every strand of DNA holds a treasure trove of deeply personal information, from our propensity for medical conditions to our ancestry to our biological family relationships. And increasingly, police are accessing and testing the DNA contained in our unavoidably shed genetic material without judicial oversight. That’s why we’re asking a court to require police to get a warrant before collecting the DNA we unavoidably leave behind.

Warrantless access to unavoidably shed DNA is just one part of a troubling trend in police investigations involving DNA. Already, in more than 60 criminal cases across the country over the last two years, police have uploaded DNA evidence found at a crime scene to enormous consumer genetic databases — such as GEDmatch and FamilyTreeDNA — in order to search for family members of a possible suspect. The databases often return likely relatives as distant as the suspect’s third cousins. Using this list of likely relatives, police start building out massive family trees based on marriage certificates, death records, and more.

Police then pare the tree down, usually by age and location, in order to identify a likely suspect (or several). Finally, police follow the suspects around until those individuals discard items containing their DNA — anything from a Baskin-Robbins spoon to a napkin to a colostomy bag adhesive patch. Without getting a warrant from a judge, police extract and test the DNA on those items, and use the resulting genetic profile to determine whether that suspect’s DNA matches the original crime scene evidence.

This practice raises profound civil liberties and privacy concerns. Law enforcement is searching through databases of thousands upon thousands of people’s highly revealing DNA profiles, and then surreptitiously collecting and testing people’s DNA without the protections and constraints of a warrant.

In a friend-of-the-court brief we filed this week together with the ACLU of South Dakota and the Electronic Frontier Foundation, we argue that law enforcement must first get a warrant before extracting and analyzing unavoidably shed DNA. The genetic blueprint we inadvertently leave behind as we discard coffee cups, toss crumpled tissues, spit out gum, or even lose hair is entitled to the full protection of the Fourth Amendment.

In the case at hand, State v. Bentaas, a South Dakota state criminal case, South Dakota police sent a DNA sample to Parabon Labs, which created a genetic profile and then ran it against GEDMatch’s database of over one million genetic profiles. The lab uncovered a few family names in South Dakota’s Sioux Falls and Hutchinson County areas and identified possible third cousins. Using this information, South Dakota detectives embarked on their own research to build out a family tree. Eventually, based on these findings, investigators identified the defendant, Ms. Bentaas, as a possible suspect.

Without first obtaining a warrant, investigators went to Ms. Bentaas’s residence and took garbage left outside for the trash collector. From the trash bag, police retrieved cigarette butts, cotton swabs, Kleenex with hair, earplugs, water bottles, glass bottles, beer cans, and dental floss. The government then extracted and analyzed the DNA found on these items. Based on the results, investigators arrested Ms. Bentaas.

To defend its warrantless search and seizure, the state is asserting that people do not have a reasonable expectation of privacy in their trash, and, therefore, people also do not have a privacy interest in the DNA they leave on discarded items. The government’s argument relies on a decades-old, flawed precedent holding that when we leave our garbage on the curb to be collected, we relinquish our Fourth Amendment privacy rights in the items contained in our opaque trash bags.

Whatever the merits of that rule as applied to physical items in the trash, it should not be stretched to permit warrantless searches of DNA. As the Supreme Court recently made clear in Carpenter v. United States, a case argued by the ACLU, old rules permitting warrantless searches cannot be automatically extended to new police capabilities made possible by modern technologies. The scope and types of information that might be discovered through a search of one’s physical trash pale in comparison to the deeply sensitive and highly personal information our genetic blueprints can reveal. And though people might sometimes be able to avoid discarding certain physical items, they cannot avoid shedding DNA on virtually every surface and object they touch. Our DNA requires greater protections under the Fourth Amendment.

The implications of the government’s argument are chilling. If police are allowed to surreptitiously extract and sequence our DNA without a warrant anytime they wish, there is little stopping them from grabbing every person’s trash, secretly extracting our DNA from it, and building a massive database containing our most sensitive genetic information. Already, local law enforcement officers have tried to track anti-pipeline protesters by swabbing cigarette butts left behind at protest sites. 

As our ability to decode DNA improves, the scope of sensitive, private information that is discernable will only increase. As it does, so will the need for strong Fourth Amendment protections to keep this information safe from warrantless searches and unconstitutional intrusion.

Alexia Ramirez, Fellow, ACLU Speech, Privacy, and Technology Project

“They did what human beings looking for freedom, throughout history, have often done. They left.”

These are the words of Pulitzer Prize-winning author Isabel Wilkerson in her book, “The Warmth of Other Suns.” The book follows the story of three Black Southerners and their journey escaping racial violence — a sharecropper’s wife who left Mississippi in the 1930s for Chicago, an agricultural worker who left Florida for New York City in the 1940s, and a doctor who left Louisiana in the early 1950s.

Their journey was part of the Great Migration that occurred between 1916 and 1970, where 6 million Black people moved out of the rural South to the urban Northeast, Midwest, and West. As a native Texan moving to Southern California, I was curious to learn more about the experience of Black Southerners who moved here before me. I learned that this region held promise of safety and security for Black people escaping the ever-present threat of violence and death in the South. But as Black families found out then and Black communities today know all too well, while the warmth of San Diego’s sun might be gentler than the heat of the South, they both cast the familiar shadow of racial violence that Black people across the country can’t escape.

As a policy associate for the ACLU of San Diego & Imperial Counties, I advocate for policies that advance police accountability. Recently, our office commissioned a report by Campaign Zero that looked at data from the San Diego Police Department and the San Diego County Sheriff’s Department and analyzed it for racial and identity disparities.

Here is what the report found:

The San Diego Police Department (SDPD):

• Stopped Black people at a 219 percent higher rate than white people. In 85 percent of SDPD beats, Black people were stopped at higher rates than white people.
• Was 23 percent more likely to conduct consent searches on Black people than white people, despite being less likely to be found with contraband than white people.
• Was more likely to use force and even more severe forms of force against Black people than white people.

The story was not any better at the county level. The San Diego County Sheriff’s Department:

• Stopped Black people at a 130 percent higher rate than white people. In every area of jurisdiction, Black people were stopped at higher rates than white people. 
• Was 19 percent more likely to search people they perceived to be LGBTQ or gender non-conforming and 38 percent more likely to arrest them without a warrant compared to people who were not perceived to be LGBTQ or gender non-conforming. This disparity was particularly worse for the Black people in this demographic.
• Used more severe levels of force against Black people and Asian/Pacific Islanders.

This is the reality that Black San Diegans, Black Californians, and Black Americans face on a daily basis. Our movement and freedom is policed more often and more severely than our white neighbors. The sad irony about Black people and families that moved to California to escape violence during the Great Migration is that they and their descendants now live in a state with the most civilian deaths caused by police violence. Of those killings, Black people are disproportionately represented.

A recent study found that nationwide, 1 in every 1,000 Black men can expect to be killed by police. In fact, 13 of the 100 largest U.S. city police departments kill Black men at higher rates than the U.S. murder rate.

Although police brutality and killings of civilians have incredible human costs, there is tremendous harm, both physical and psychological, inflicted by even the most routine police activity. Across the country, law enforcement agencies regularly monitor, harass, profile, stop, search, question, detain, and arrest Black people at rates completely disproportionate to their population.

Just as laws were used to respond to the violence of Jim Crow, we also need laws that protect Black communities from racially disparate policing. California has begun to make headway in this regard by passing AB 392: The California Act to Save Lives, which created a higher, “necessary” standard for when police can use force. Now, we need to raise the standard for when police can stop and search people — in California and across the country.

America has begun to begrudgingly recognize Black people’s humanity, freedom, and civil rights. And yet, there is still so much work to do. When I feel discouraged by the slow progress of racial justice, I find comfort in the words of the Black National Anthem, written just before the start of the Great Migration.

It goes:

Sing a song full of faith that the dark past has taught us,

Sing a song full of hope that the present has brought us,

Facing the rising sun of our new day begun,

Let us march on till victory is won.

From calling on city leaders to address biased policing to fighting law enforcement’s use of intrusive surveillance technology (i.e., smart streetlights), San Diegans — in solidarity with communities across the country — are marching boldly, loudly, and unapologetically toward that day where freedom also includes freedom of Black movement.

Chelsey Birgisdóttir, Policy Associate, ACLU of San Diego & Imperial Counties