Okay, so it's been a minute since I took Criminal Law; I did go back to my coursework as a refresher before posting. This is the first 'legal' post I've made since getting verified, so I'm a bit terrified, and I want to preface this with MOO to be safe.
I don't think “
fruit of the poisonous tree,” or even the broader exclusionary rule would apply to the familial DNA obtained in this case for several reasons.
First, as far as we know, LE obtained the familial DNA legally. They
had a warrant--obtained before they had the DNA evidence-- which allowed them to go through the trash at the family home in PA. I believe they didn't need a warrant to go through the trash as long as it had been put out for collection (see
CA v. Greenwood) but MSM is reporting that they did obtain one.
Second, and I think you know this, FamilyTreeDNA and GEDMatch (the two DNA databases available to law enforcement) both indicate to users uploading data that they are searchable by LE; in one of them (I forget which), the user actually has to check a box to opt in to LE searches. We don't know which database LE used here, or if they used one at all. Current PA law
allows for an exception to confidentiality in genetic testing when, pursuant to a court order (here, the warrant), a court determines it will produce information relevant and material to a matter before the court (here, a familial genetic match to the suspect in a quadruple homicide). As a side note, there is
a stricter bill, introduced in the PA house last year, which does not appear to have made it out of committee. All LE needed for the arrest warrant was probable cause, and the legitimately acquired familial DNA gave them that. The prosecution is not going to use the familial DNA at trial; they will use the DNA taken from BK after he was brought into custody, which will be an absolute match to the snap on the knife sheath, rather than a match to the paternal line of the person whose DNA is on the sheath. Using familial DNA to identify a suspect is different than introducing it as evidence at trial.
Lastly, FOPT also doesn't always apply when evidence was gathered in good faith, even if the evidence used to produce it is excluded--so if the defense argues that the warrant that allowed LE to collect the trash was invalid, and the court agrees, the DNA obtained by going through the trash is potentially still admissible because LE followed the proper procedures, got their warrants, and were acting in good faith.
I'm sure there are some nuances I'm missing, but hope this was useful.
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MOO.