You had William Santiago's letter.
4 seconds sound clip from the A Few Good Men movie soundboard.
You can hear this line at 01:09:52 in the Blu-ray version of the movie.
Quote context
[...]
- Lance Corporal Dawson's been charged with a number of crimes.
- Why wasn't he charged with firing at the enemy without cause?
- There wasn't enough evidence to support such a charge.
- You had William Santiago's letter.
- And now we will never know, will we?
- No.
- Corporal Carl Edward Hammaker, Marine Barracks
- Rifle Security Company Windward, Second Platoon Bravo. (2)
[...]