I'm being dragged into a high profile case as a character witness.

In short, a guy I know had a heart attack while driving and went off the road hitting multiple people and killed someone. He's being charged as if he intentionally did it with a hate crime included.

The prosecuting attorney is known to be corrupt but has ultimate power. No lawyer in town is willing to take the case so they had to get a lawyer out the area and are being funded by outside the state resources. Anybody who is helping the defense will be a "marked man." Fine whatever, but what I most worried about is my employers lawyers are heavily connected to the prosecutor.

Is there any problem with me writing a character reference letter? If I write a letter what are the chances I'm going to be put on the stand?