YMMV / Law & Order S16E12 "Family Friend"

• Magnificent Bastard: Valerie Messick is the widow of mob accountant Phillip Messick who's brutally murdered by thug Jay Fleckner who also attacks and almost kills her too. Wanting to make Fleckner pay, Valerie asks close friend Bob Cerullo—a former cop—to kill him and throws her testimony in court to make it look like she couldn't positively identify Fleckner so that he'd be acquitted. This results in Cerullo killing Fleckner and staging the scene to look like self-defense. Once Cerullo is on trial though, Valerie is discovered in her husband's book under different names and only agrees to testify and reveal what she knows if she's given full immunity before saying anything at all. She then testifies reluctantly resulting in Cerullo being found guilty and Valerie getting away with everything.