Why does the FBI want to take a look inside your iPhone?

Why does the FBI want to take a look inside your iPhone?

The FBI wants the encryption keys to the iPhone, yet has a poor track record since September 11, 2001 of protecting Constitutional rights.

After an inexplicable and terrible crime was committed in December, leaving 14 dead and 22 injured in California, the public was informed that an act of terror had been committed. We were told that the culprits were a San Bernardino County Health Department employee and his wife who were killed after they fled the scene.