Just to add to the solutions above, if you miss the cue like I did as I was talking in my Twitch stream then don't worry after he kills himself the inspector will come in and then you're asked if you want to see a different ending or if you want to end that case. Hit
to see a different ending and you will go back to making the moral decision in the
deduction tab and you'll be able to try again as many times as you need :)