The OIA documents - released alongside his statement - said the visitor-prisoner ID system at Auckland Prison would store people's photos and use them, along with their fingerprints, "for comparison against future entries of the individual".
RNZ has asked Corrections to clarify how the biometrics system stores photos, but does not run facial recognition.
Fingerprint recognition was used "but it is made clear to all visitors on arrival at a prison that this is not compulsory and other forms of identification are available", Robertson said in his statement.
The Auckland Prison visitor system provided by Honeywell had no connection with any other network and could not be accessed remotely, he said.
A privacy impact assessment in 2018 found this system was "a low privacy risk".
Corrections has not said if such an assessment, in use since 2015, was carried out at privately-run Auckland South.
There, Serco holds the contract for the biometrics system with provider SAAB.
The privacy impact assessment said visitors would get a wrist band with a Q code on it.
"The Q code is a representation of their ID but does not contain personal information.
"Where individuals are unwilling to provide biometric information, a secondary credential process that allows staff to verify 'face to photo' is available."
Biometric data was purged at set expiry dates.
The overall biometric system used for prisoners is supplied by Biolink Solutions, which Corrections has paid $779,000 in a five-year contract that runs to July next year.
However, as for total biometrics spending: "Corrections is not able to provide a reliable figure... as these costs are in many cases not separately identified from the cost of other services provided by vendors supplying or supporting the deployment of this technology."
It was fundamental that biometric data was handled in accordance with privacy laws, Roberston said.
- RNZ
