Junk DNA (Literally) in Virginia

The Washington Post reported yesterday on a motion in Alexandria Circuit Court to suppress "all evidence flowing from the warrantless search of [Jesse Bjerke's] genetic profile." 1/ Mr. Bjerke is accused of raping a 24-year-old lifeguard at gunpoint at her home after following her from the Alexandria, Va., pool where she worked. She "could describe her attacker only as a thin man she believed was 35 to 40 years old and a little over 6 feet tall." 2/ Swabs taken by a nurse contained sperm from which the Virginia Department of Forensic Sciences obtained a standard STR profile.

Apparently, the STR profile was in neither the Virginia DNA database not the national one (NDIS). So the police turned to the Virginia bioinformatics company, Parabon Labs, which has had success with genetic genealogy searches of the publicly available genealogy database, GEDmatch. Parabaon reported that

[T]he subject DNA file shares DNA with cousins related to both sides of Jesse's family tree, and the ancestral origins of the subject are equivalent to those of Jesse. These genetic connections are very compelling evidence that the subject is Jesse. The fact that Jesse was residing in Alexandria, VA at the time of the crime in 2016 fits the eyewitness description and his traits are consistent with phenotype predictions, further strengthens the confidence of this conclusion.

Recognizing the inherent limitations in genetic genealogy, Parabon added that

Unfortunately, it is always possible that the subject is another male that is not identifiable through vital records or other research means and is potentially unknown to his biological family. This could be the result if an out-of-wedlock birth, a misattributed paternity, an adoption, or an anonymous abandonment.

The motion suggests that the latter paragraph, together with the firm's boiler-plate disclaimer of warranties and the fact that the report contains hearsay, means that police lacked even probable cause to believe that the sperm came from the defendant. This view of the information that the police received is implausible, but regardless of whether "the facts contained in the Parabon report do not support probable cause," 3/ the police did not use the information either to arrest Mr. Bjerke immediately or to seek a warrant to compel him to submit to DNA sampling. Instead,

Police began following Bjerke at his home and the hospital where he worked as a nurse. They took beer bottles, soda cans and an apple core from his trash. They tracked him to a Spanish restaurant ... and, after he left, bagged the straws he had used.

The DNA could not be eliminated as a match for the sperm from the rape scene, a forensic analysis found, leading to Bjerke’s indictment and arrest in February. With [a] warrant, law enforcement again compared his DNA with the semen at the crime scene. The result: a one in 7.2 billion chance it was not his. 4/

A more precise description of the "one in 7.2 billion chance" is that if Mr. Bjerke is not the source, then an arbitrarily selected unrelated man would have that tiny a chance of having the STR profile. The probability of the STR match given the hypothesis that another man is the source is not necessarily the same as the probability of the source given the match. But for a prior probability reflecting the other evidence so far revealed about Mr. Bjerke, there would not be much difference between the conditional probability the laboratory supplied and the article's transposed one.

Faced with such compelling evidence, Mr. Bjerke wants it excluded at trial. The motion states that

For the purposes of this motion, there are three categories of DNA testing. (1) DNA testing conducted before Jesse Bjerke was a suspect in the case; (2) DNA testing conducted without a warrant after Jesse Bjerke became a suspect in the case; and (3) DNA testing conducted with a warrant after Jesse Bjerke's arrest. This motion seeks to suppress all DNA evidence in categories two and three that relate to Jesse Bjerke.

An obstacle is the many cases -- not mentioned in the motion -- holding that shed or "abandoned" DNA is subject to warrantless collection and analysis for identifying features on the theory that the procedure is not a "search" under the Fourth Amendment. The laboratory analysis is not an invasion of Mr. Bjerke's reasonable expectation of privacy -- at least, not if we focus solely on categories (2) and (3), as the motion urges. This standard STR typing was done after the genetic genealogy investigation was completed. The STR profile (which the motion calls a "genetic profile" even though it does not characterize any genes) provides limited information about an individual. For that reason, the conclusion of the majority of courts that testing shed DNA is not a search is supportable, though not ineluctable. ("Limited" does not mean "zero.")

Indeed, most laboratory tests on or for traces from crimes are not treated as searches covered by the warrant and probable cause protections. Is it a search to have the forensic lab analyze a fingerprint from a glass left at a restaurant? Suppose a defendant tosses a coat in a garbage bin on the street, and the police retrieve it, remove glass particles, and analyze the chemical composition to see they match the glass from a broken window in a burglary? Did they need a warrant to study the glass particles?

The underlying issue is how much the constitution constrains the police in using trace evidence that might associate a known suspect with a crime scene or victim. When the analysis reveals little or nothing more than the fact of the association, I do not see much of an argument for requiring a warrant. That said, there is a little additional information in the usual STR profile, so there is some room for debate here.

However, this case might be even more debatable (although the defense motion does not seem to recognize it) because of category (1) -- the genetic genealogy phase of the case. The police, or rather the firm they hired to derive a genome-wide scan for the genetic genealogy, have much more information about Mr. Bjerke at their disposal. They have on the order of a million SNPs. In theory, Parabon or the police could inspect the SNP data for medical or other sensitive information on Mr. Bjerke now that he has been identified as the probable source of those sperm.

Nevertheless, I do not know why the police or the lab would want to do this, and it has always been true that once a physical DNA sample is in the possession of the police, the possibility exists for medical genetic testing using completely different loci. Testing shed DNA in that way should be considered a search. Bjerke is a step in that direction, but are we there yet?

The Post's online story has 21 comments on it. Not one supported the idea that there was a significant invasion of privacy in the investigation. These comments are a decidedly small sample that does not represent any clear population, but the complete lack of support for the argument that genetic genealogy implicates important personal privacy was striking.

NOTES

1. Defendant's Motion to Suppress, Commonwealth v. Bjerke, No. CF19000031 (Cir. Ct., Alexandria, Va. May 20, 2019).
2. Rachel Weiner, Alexandria Rape Suspect Challenging DNA Search Used to Crack Case, Wash, Post, June 10, 2019, at 1:16 PM.
3. Defendant's Motion, supra note 1.
4. Weiner, supra note 2.

RELATED POSTING

• Trawling Genealogy Databases and the Fourth Amendment: Part I, June 23, 2018, http://for-sci-law.blogspot.com/2018/06/trawling-genealogy-databases-and-fourth.html

ACKNOWLEDGMENT

• Thanks to Rachel Weiner for alerting me to the case and providing a copy of the defendant's motion.