Microscope Monday: Analysis of Massachusetts’ proposed License Plate Privacy Act, H 3068 / S 1648


One of the curious things about digitization is that it allows data to be circulated and shared almost effortlessly. New, cheap ways of sharing and storing data can turn data collection that was previously quite innocent into a serious threat to our ability to be free from government surveillance.

Historically, the law has recognized no constitutional issue with law enforcement collection of license plate numbers, because cars are normally out in public when the numbers are collected. But what happens if cop cars can collect every license plate from every car they pass, moving or parked; check the plate against a database of outstanding warrants; link them to GPS coordinates; and retain the records of which car was where forever, so that they can retrospectively construct a map of your movements?

Well, folks, that bright new day is here. The devices are called “automated license plate readers”, or ALPRs for short. And the ACLU of Massachusetts is supporting a bill that tries to grapple with their implications, and that received its first Joint Committee on Transportation hearing on May 16.

The legislation codifies the uses of ALPR technology. As described by the ACLU, it prohibits:

all uses of ALPRs except for electronic toll collection, parking enforcement, controlling access to “secured areas”, and by police for “immediate comparison” of ALPR data with certain law enforcement databases for limited purposes. […] For the police to retain the data for longer than 48 hours, they would have to seek a search warrant. […] License plate information collected in violation of the statute would not be admissible by the prosecution at trial and the prosecution would have the duty to turn over all ALPR data to the defense. ALPR data would also be deemed “personal information” so it would come under the protection of the fair information practices laws. […] Finally, no entity is allowed to “sell, trade, or exchange” ALPR data.

The “limited purposes” refer mainly to the “amber alert” system for missing children and the “silver alert” system for identifying cars belonging to people with outstanding arrest warrants. The key to this provision, though, is specifying that the data can be used only for “immediate” comparison, and then must be destroyed. This would make it impossible to construct retrospective maps of where particular cars have gone.

We have seen in the recently decided Jones case that the Supreme Court has recognized a Fourth Amendment interest that may require a search warrant in otherwise innocuous data that tracks a car’s movements over a period of 28 days, though that ruling left ambiguous whether data collected over, say, seven days, or 10, or 14, would similarly require a warrant.

The police would be allowed to collect ALPR data and then apply for a warrant to keep it for longer than 48 hours, and that does present an issue with the Fourth Amendment, which requires a warrant to be issued before law enforcement collects the data. However, the courts have been casual enough about enforcing this aspect of the Fourth Amendment that this provision would probably survive litigation.

The bill requires law enforcement’s uses of ALPR technology to be regularly reported to the public: the number of plates scanned, the number of data preservation requests, the number of disclosure orders, any changes in policy on the use of ALPRs that would affect privacy, and the number of convictions obtained through the use of ALPR data. Similar disclosure requirements currently exist for the uses of electronic wiretapping warrants under Massachusetts General Laws chapter 272.99. However, as with the wiretapping laws, the most interesting data is not reported, which would be data enabling a cost-effectiveness analysis. It would be great if the data reporting requirements included how much law enforcement was spending on ALPR software and equipment, so that the public could also assess how much was being spent in order to secure what kinds of convictions.

To sum up, this seems like a bill well worth supporting. It imposes reasonable limitations to discourage misuse of ALPR technology, while still allowing on-the-spot use that has limited implications for the Fourth Amendment.

List of bills’ cosponsors:
Jonathan Hecht, Josh S. Cutler, William N. Brownsberger, Martha M. Walz, Kay Khan, Peter V. Kocot, James J. O’Day, David M. Rogers, Paul McMurtry, Ruth B. Balser, Timothy J. Toomey, Carl M. Sciortino, Benjamin Swan, Brian R. Mannal, Christine E. Canavan, Anne M. Gobi, Denise Andrews, John W. Scibak, Michael Barrett, Frank I. Smizik, Diana DiZoglio, Viriato M. deMacedo, Denise Provost, Harold P. Naughton, Cory Atkins, Thomas P. Conroy, Jason M. Lewis, Antonio F. Cabral, Kenneth I. Gordon, Tom Sannicandro.

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