Would you kill an innocent person if you thought it might mean saving a dozen other people?

If it caused harm to other people then that person isn't technically innocent. So you'd be saving people and getting harm out of the way. Depending on the reason maybe. As long as I wouldn't get in trouble for it. 

This is a philosophy question that is often posed as in the form of the trolley problem.  There is no right or wrong answer to this.

However, there are the two different viewpoints on the topic.

If a person likes utilitarian ideals, then they most likely will see that killing one person is better than killing a dozen people.

However, things can be affected if a person has to actually make the choice for them to kill the person or if they should just let the killing of the dozen take course.