You should never blame someone else for your mistakes.
Tom is a team leader has made a serious error in the important team project that was just submitted.
Tom wants to avoid getting in trouble at work.
Tom works extra hours to fix the mistake on his own time and explains it to his boss.
Tom tells his superiors that one of his colleagues, rather than him, was in charge of that part of the project.
Tom protects his team from disciplinary action.
Tom gets someone else in trouble for their mistake.