That is exactly what the CIA has done:
The CIA destroyed videotapes it made in 2002 of two top terror suspects because it was afraid that keeping them "posed a security risk," Director Michael Hayden has told agency employees.
Hayden's revelation to the CIA employees became public Thursday and it caused a commotion on Capitol Hill where members of the Senate Intelligence Committee immediately vowed to conduct a thorough review. A leading human rights group voiced alarm about it.
In his message to agency workers, Hayden said that House and Senate intelligence committee leaders had been informed of the existence of the tapes and the CIA's intention to destroy them to protect the identities of the questioners. He also said the CIA's internal watchdog watched the tapes in 2003 and verified that the interrogation practices were legal. Hayden said the tapes were destroyed three years after the 2002 interrogations.
If you or me destroyed evidence we would face criminal charges. Some how I doubt that will be the case. In our corrupt capital, the rule of law takes the backseat to everything else.