"Are you going to let this killer's love go to waste?"
As he sat across from Will, Hannibal searched in his face for softening of the eyes, or a soft reverential breath, or the upturned corner of the lips; but he saw nothing apart from the furrowed brow and hard lines in his tired face. It did not seem Will was open to the idea even slightly, or that he had the capacity to be.
In his stomach he felt something unsettling, and it made him uncomfortable. In his mind he saw flashes of that woman, and her angry eyes that refused to meet his. At least Will would look. Will was looking at him, now, right in the eyes. But his eyes were blank, and so Hannibal kept searching in Will's face for something different. He did not see anything, and it made him uncomfortable.
So Hannibal realized that he had some work to do, as far as Will was concerned. He had-erroneously-assumed that Will's time in jail would soften him a bit, or at least act as a catalyst for the re-examination of what he thought he knew; he expected, at the least, a little more open-mindedness from the man. But it had not come, at least not yet. Worse still, Will was tense and reticent-even when he was around.
So Hannibal's decision to testify was twofold: to remind Will that he was there for him, and also to remind him why he was there.