dead man walking
1. A (male) prisoner on death row who is walking to the place of execution. Primarily heard in US, South Africa. It's been my duty to accompany each dead man walking as he takes his last steps in this world.
2. By extension, any man who is in great trouble or difficulty and is certain to face punishment, especially the loss of a job. John really screwed up that business deal; I'd say he's a dead man walking at this point. I lost all of our savings in the casino last night—I'm a dead man walking.
3. Any man who is near death or certain to die. They just discovered that I've got cancer, and it's already spread to my lymph nodes—I'm a dead man walking. Don't worry about him, he's a dead man walking; we'll make sure that stool pigeon never talks.