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(i.e., a “cluster”). It is possible to identify a district court denied the motion. Gratkowski
“cluster” of Bitcoin addresses held by one entered a conditional guilty plea to both counts,
organization by analyzing the Bitcoin blockchain’s reserving the right to appeal the denial of his
transaction history. Open source tools and private motion to suppress. After the district court issued
software products can be used to analyze a its final judgment, Gratkowski timely appealed.
transaction.
“We will uphold a district court’s denial of a
2 Blockchain is a technological advancement that suppression motion if there is any reasonable view
permits members in a shared network to “record a of the evidence to support [the denial].”
history of transactions on an immutable ledger.”
See Ashley N. Longman, Note, The Future of Gratkowski presents the novel question of whether
Blockchain: As Technology Spreads, It May an individual has a Fourth Amendment privacy
Warrant More Privacy Protection for Information interest in the records of their Bitcoin transactions.
Stored with Blockchain, 23 N.C. BANKING INST. 3 For the Government to have infringed upon an
111, 118–19 (2019) (citing Brittany Manchisi, individual’s Fourth Amendment protection against
What is Blockchain Technology?, BLOCKCHAIN unreasonable searches, the person must have had a
PULSE: IBM BLOCKCHAIN BLOG (July 31, “reasonable expectation of privacy” in the items at
2018), issue.
https://www.ibm.com/blogs/blockchain/2018/07/w
hat-is-blockchain-technology/). 3 So far, we have found only two other federal
district courts (and no circuit courts) that have
Federal agents used an outside service to analyze addressed the issue of whether an individual has a
the publicly viewable Bitcoin blockchain and privacy interest in the records of their Bitcoin
identify a cluster of Bitcoin addresses controlled by transactions on a virtual currency exchange. See
the Website. Once they identified the Website’s Zietzke v. United States (Zietzke II), No. 19-cv-
Bitcoin addresses, agents served a grand jury 03761, 2020 WL 264394 (N.D. Cal. Jan. 17, 2020);
subpoena on Coinbase—rather than seeking and Zietzke v. United States (Zietzke I), 426 F. Supp. 3d
obtaining a warrant—for all information on the 758 (W.D. Wash. 2019). In each case, the district
Coinbase customers whose accounts had sent court held that the defendant did not have a privacy
Bitcoin to any of the addresses in the Website’s interest in their Bitcoin transaction records because
cluster. Coinbase identified Gratkowski as one of the transactions were shared with a third party, the
these customers. With this information, agents virtual currency exchange. Zietzke II, 2020 WL
obtained a search warrant for Gratkowski’s house. 264394, at *13; Zietzke I, 426 F. Supp. 3d at 768-
At his house, agents found a hard drive containing 69.
child pornography, and Gratkowski admitted to
being a Website customer. Under the third-party doctrine, a person generally
“has no legitimate expectation of privacy in
The Government charged Gratkowski with one information he voluntarily turns over to third
count of receiving child pornography and one parties.” But relying on Carpenter v. United States,
count of accessing websites with intent to view which limited the applicability of the third-party
child pornography. Gratkowski moved to suppress doctrine in the context of cell phones, Gratkowski
the evidence obtained through the warrant, arguing argues that the Government violated his reasonable
that the subpoena to Coinbase and the blockchain expectation of privacy in the records of his Bitcoin
analysis violated the Fourth Amendment. The transactions on (1) Bitcoin’s public blockchain and
Nov.-Dec. 2021 www.texaspoliceassociation.com • (512) 458-3140 27
