Security researchers at the University of Erlangen-Nuremberg in Germany have shown that they can extract photos, surfing history, and contact lists from Android smartphones, even if the phone is locked and the disk is encrypted. It can take anywhere from a few seconds to a few minutes for RAM to lose its data. One of the variables that causes this variance is temperature; by cooling RAM down, it preserves data for longer.

http://www.extremetech.com/computing/150536-how-to-bypass-an-android-smartphones-encryption-and-security-put-it-in-the-freezer