He says that if you do accept under his specific conditions, he will sign a full confession, plead guilty right now.
6 seconds sound clip from the Se7en (1995) movie soundboard.
You can hear this line at 01:37:59.141 in the Blu-ray version of the movie.
Quote context
[...]
- We don't make deals here, Mr. Swarr.
- My client also wishes inform you that if you do not accept he will plead insanity across the board.
- Let him try it. I'd like to see him try.
- I'm not letting this conviction slide. I can tell you that.
- It's your case. Make a decision.
- It has to be the both of you.
- If he were to claim insanity, this conversation is admissible.
[...]