Ready or Not

After my first mission, the evidence locker was unlocked. Before the first mission it was cordoned off.

When I entered the locker downstairs, I could interact with some boxes on the left of the first desk you encounter before stepping through the gate to the actual evidence room.

When you start the single player (I chose commander) you start in the HQ. At this time you have limited access to the HQ, the evidence locker is cordoned off. There is a sign that says evidence locker above the entrance.

After my first mission (single player/commander), the evidence locker was unlocked.

When I entered the locker downstairs, I could interact with some boxes on the left of the first desk you encounter before stepping through the gate to the actual evidence room.