Normally, I weigh in on the side of individual privacy... but
I consider this information to be relatively public by nature and there are considerable benefits to having this type of system in place.
Ex:
Resolving amber alerts faster, Locating stolen vehicles faster, Improved efficiency of local governments, etc...
Balancing the need for individual privacy/rights with protecting the individual rights of other citizens, while operating within a limited budget is a tricky thing. The need to avoid the "slippery slope" is great, and the loss of individual privacy should always be considered a great cost, but a cost-benefit analysis should be done. The following should be kept in mind though:
1.) Individual privacy is not priceless.
(How much Individual Privacy have some people freely given up just to use facebook?)
2.) How does the cost of hiding information like X impact the individual rights of others?
City budget cuts are pretty common these days and often translate to fewer police. I would argue that a system like this could improve efficiency and help lessen the impact of cuts like these.
I believe the information should be purged when it is older than 2 months in order to help limit the scope of the system to a near-time discovery tool as oppose to a long-term tracking mechanism.