Data from more than 68,000 Boston Police Department automated license plate reader scans — a fraction of the total scans the department has performed since 2006 — show the department’s program violated its own rules and failed to effectively follow up on leads that had been flagged dozens of times.

A report released yesterday by the ACLU breaks down the widespread law enforcement use of automated license plate readers across the country. Our users have obtained hundreds of pages of documents on this controversial technology.

In a collaboration with the Boston Globe, MuckRock requested documents detailing the use of automated license plate recognition (ALPR) scanners from more than 50 police agencies in Massachusetts. Fewer than a third of departments have formal, written standards to govern use of ALPR and plate scan data. Those that do have policies vary widely on details.

Automatic license plate reader (ALPR) technology is among a new generation of law enforcement tools that enables police to scan the plate of any car that passes. In Somerville, Mass., aldermen are now asking questions after a MuckRock request revealed ALPR had been used without a written policy addressing privacy issues.

In a September 2011 memo released to MuckRock, Boston Police Department Commissioner Edward Davis outlines how BPD and its officers are authorized to use automated license plate recognition (ALPR) technology and data. In particular, the memo reveals BPD’s capacity to retain ALPR data indefinitely for investigatory purposes.