Principle of double effect

The principle of double effect is a set of ethical criteria for evaluating the permissibility of acting when one’s otherwise legitimate act (for example, relieving a terminally ill patient’s pain) will also cause an effect one would normally be obliged to avoid (for example, the patient’s death.)

- The act itself must be good

- The bad effect cannot be the means to good

- You must have a good intention. The bad bit must be a side-effect.

- Total good must be greater than total bad.

http://en.wikipedia.org/wiki/Principle_of_double_effect