Feature of database-level audit in SQL Server 2012 Express edition
Old question, but since it got bumped I will answer with some updated information. 

While Express 2012 was limited to server level auditing (referred to as "basic auditing" in feature comparison documentation) and its RTM SSMS version was limited in GUI functionality for auditing, newer versions have removed both of those limits:


The newest 17.x versions of Management Studio are 100% compatible with SQL 2012 (and every subsequent version) and has no GUI-based limitation on auditing features (assuming they're supported by the SQL Server version it is connecting to). 
As of SQL Server 2016 SP1, "fine grained auditing", i.e. database level auditing, is available across all SQL Server editions. 


The term "fine grained auditing" is strange in context of SQL Server, as it seems to only be used in feature comparison docs by Microsoft, but not in any other documentation.

Additionally, I have written a distilled comparison of key features across different editions and versions of SQL Server, focusing on the perspective of Express.