It's been bugging me for a long time. Please help!

Trying to identify a film. Fairly sure a police officer has been killed. There's a funeral. The widow says to the murdered officer's partner 'you don't arrest him, you hear me? You don't arrest him', clearly telling the partner to make sure whoever did it is killed. if anyione has any idea? I thought it might be Insomnia, but AI is adamant is isn;t, and it seems very hard to actually watch to find out!