Unless you're hired by the chief of police, that sounds very close to testing a system - the police - without the permission of the owner?
And there are safer ways to find the police's reaction time than having them turn up with guns drawn, finding signs of forced entry, and finding you - a non-employee - sneaking around with burglary tools.
For example, you could make a FOIA request for their internal records, ask a local journalist - or if you insist on a real-world test, have the alarm 'accidentally' tripped by a legitimate employee arriving for work early.
And there are safer ways to find the police's reaction time than having them turn up with guns drawn, finding signs of forced entry, and finding you - a non-employee - sneaking around with burglary tools.
For example, you could make a FOIA request for their internal records, ask a local journalist - or if you insist on a real-world test, have the alarm 'accidentally' tripped by a legitimate employee arriving for work early.