父母移民急問

母親年邁，指紋不清,   今天收到appointment letter from USCIS

Reason for Appoinment:   Sworn statement for unclssfied prints
Bring with you:                   Identification and a POLICE CLEARANCE LETTER FROM THE PRECINCT(S) WHERE YOU HAVE   RESIDED FOR THE LAST FIVE YEARS.


時間就在7天後。

請問
1. 這是做什麽？
2. 關於“POLICE CLEARANCE LETTER FROM THE PRECINCT(S) WHERE YOU HAVE   RESIDED FOR THE LAST FIVE YEARS.” 我母親最近一年住在美國，是否可已 get the letter from the local police dept?  還需要從中國開信嗎？ 可時間太緊了。