Incidents are being missed and evidence lost because of technical problems with Dunedin's ratepayer-funded CCTV system.
The concerns have prompted a Dunedin City Council staff investigation into ways of improving the system and the likely cost.
The network of 14 security cameras was installed in the Octagon last year at a cost of $200,000, with ratepayers paying $150,000 of the bill and community organisations the rest.
However, a police report to the council's community development committee has raised concerns about aspects of the camera system's performance, even while praising overall results.
The report, by Senior Constable Niall Shepherd, warned limited storage capacity at the Dunedin Central Police Station meant a 3 week limit on the time images could be kept before being overwritten.
That was "probably the absolute minimum" needed by police and resulted in "disappointment" for some staff because of the time taken to launch some investigations and seek images, he said.
The secure wireless connection between the police station and the Civic Centre was also causing problems.
The images were viewed in real time by a team of volunteers at the police station, but the limited capacity of the wireless link, combined with low-light conditions at night, was creating a "bottleneck" and delays between images, he said.
"This gives the effect of time-lapse photography, where there can be some seconds of delay between images, making it very frustrating to watch.
"Often, detail of incidents, and sometimes entire incidents, are missed as the download catches up."
The problems were fuelling "a lack of confidence in the system by the uninformed" and a solution should be investigated, he said.
However, addressing last week's committee meeting, Dunedin-Clutha police area commander Inspector Dave Campbell said the cameras remained an "excellent" system despite the glitches.
The cameras were activated last October and by May 9, volunteers monitoring them had detected 54 offences, nearly half involving violence and mainly occurring early on Friday, Saturday and Sunday mornings.
In some cases, officers were able to catch offenders still at the scene, he said.
"There's numerous examples of how we have had success in terms of investigations and we have come across assaults that weren't reported to us."
Evidence gathered using the cameras had contributed to 23 prosecutions, although it was difficult to track outcomes because the court process could take months.
Council customer advocate Adrian Blair said the storage capacity issues related to the resolution of images - which dictated their size and usefulness to police - and it was "very much a balancing act".
The council investigation would look at using a fibre link to the police station and the likely cost, he said. It would also consider making better use of compression and other initiatives to increase transfer speeds and storage capacity.
