I don't think you can break a lease because someone across the street is a thief... But, take a close look at your lease and any buidling security clauses in it, and then look at your city's building codes and any required security measures the landlord MUST provide. If the building meets all codes, and the terms of your lease have been met, you're pretty much at the mercy of your neighborhood! You cannot expect a landlord to be responsible for the folks across the street, can you? If, on the other hand, your city REQUIRES a locked front access, and your building's door is open, you may be able to show cause to break the lease.
Add neighborhood crime reports to things to check out BEFORE you sign a lease, folks!
As with mud, life, too, slides by.