ALPR Data Retention and Sharing

Who decides how long data is kept

Retention is set by the customer agency, “based on its own policy and applicable law,” according to Flock. After that period, Flock says the data is “permanently deleted and irrecoverable unless it has been preserved as evidence for an ongoing investigation.” In August 2026, Flock cut its recommended default from 30 days to seven. Existing customers kept the periods already approved in their jurisdictions.

State law can set limits. Knoxville’s policy, citing Tennessee law, says captured plate data “shall not be stored for more than thirty (30) days unless the data is retained or stored as part of an ongoing investigation” (¶ 29). In that case the data is destroyed when the investigation ends without charges, or at the end of any criminal action. In 2020 the California State Auditor found that retention periods “vary widely” and recommended that the Legislature set a maximum.

Preserving records past the retention period

Records connected to an investigation can be kept longer, but someone has to act. Flock described a feature called Evidence Mode that lets detectives preserve specific records tied to an active investigation. It requires the investigator to identify and preserve the record before the retention period expires. That means the records in a case file are the ones police chose to keep. Other reads that might help the defense, such as the same car seen elsewhere at the same time, may have been deleted on schedule.

Who else can see the data

Flock says data “is owned by the customer,” that customers “choose whether to share LPR data with other customers,” and that nothing is shared unless they turn sharing on. Flock’s policy also says Flock may disclose data if legally required or to comply with legal process. Its August 2026 changes gave agencies more control over which offenses other agencies may investigate using their data.

In practice, sharing can be broad. The California State Auditor found that Fresno and Marin had arranged to share their ALPR images “with hundreds of entities and Sacramento with over a thousand entities across the United States,” without evidence that the agencies had always determined whether each recipient had a right and a need to access them, or even was a public agency. California law, the Auditor noted, allows sharing only with public agencies.

Some agency policies add their own controls. Knoxville requires a lieutenant’s approval for searches run on behalf of another agency (¶ 15a).

Why retention and sharing matter in a case

• Gaps in the record. If only selected reads were preserved, the record may be incomplete. The defense may want to know what was available and what was deleted.
• Lost evidence. The constitutional duty to preserve evidence is limited. In Arizona v. Youngblood (1988), the Supreme Court held that failing to preserve “potentially useful evidence” doesn’t violate due process unless the defendant shows bad faith. Asking early for preservation matters more than relying on that rule. See requesting ALPR records in discovery.
• Out-of-area searches. If an agency elsewhere searched or supplied the data, its policy and state law may differ from the local agency’s.
• Policy compliance. Whether the data was kept or shared outside policy or state law can matter, though a policy violation doesn’t automatically make evidence inadmissible.