You heard it from the defendant's own lips.
5 seconds sound clip from the Reefer Madness (1936) movie soundboard.
You can hear this line at 00:48:27 in the Blu-ray version of the movie.
Quote context
[...]
- But the defense has been unable to prove that he was insane.
- William Harper was sane when he visited the apartment where the tragedy occurred.
- He was on the habit of visiting the place.
- He was sane when he went to a bedroom with another young woman.
- You all heard what went on in that room.
- You heard it from the defendant's own lips.
- Involved as he was in a tawdry love affair, Mary Lane was in the way.
- In a moment of anger, he deliberately and willfully killed her.
[...]