Full Idea
It is suggested the double effect act requires 1) the act is good, 2) the bad effect is not intended, and is avoided if possible, 3) the bad effect doesn't cause the good result, 4) the good must outweigh the bad side effect.
Gist of Idea
Double effect acts need goodness, unintended evil, good not caused by evil, and outweighing
Source
Thomas Mautner (Penguin Dictionary of Philosophy [1996], p.151)
Book Reference
Mautner,Thomas: 'Dictionary of Philosophy' [Penguin 1997], p.151
A Reaction
It is suggested that these won't work for permissibility of an action, but they might be appropriate for blameworthiness. Personally I am rather impressed by the four-part framework here, whatever nitpicking objections others may have found.