Most people are shocked to learn that the FBI has until this year refused to record investigations. By not recording investigations, a jury will hear only the FBI agent's summary of what was said, not what was actually said, and that is how the FBI liked it.
But things change. The FBI says they will now start recording interrogations "when possible." Now if only state and local law enforcement would follow suit, we would all be better off.
Forbes has a long piece here.