Many people consider their safe deposit boxes private. However, the boxes can be opened in certain cases.
Safe Deposit Access
For the most part, a safe deposit box is accessible only to the owner of the box and his or her designated representatives. However, if police department officials can show reasonable cause for why they believe you are involved in some sort of illegal activity, they may be able to convince a judge to allow them access to the safe deposit box, which will then be accessed by any means necessary in order to get to the contents.
With the IRS, it works a little differently. They will not take such measures; however, when there is a dispute between you and the IRS, they can issue an order freezing your assets, which will include any safe deposit boxes that you may have.
What about Others?
In some cases, if others are able to prove to a judge that you owe a debt and are hiding assets within the safe deposit box, the judge may then issue an order giving access to the contents.