A really clever deontic theory either doesn't permit those conflicts, or has a meta-rule that tells you what to do when they happen. (My favored solution is to privilege the null action.)

A deontic theory might take into account your probability assessments, or ideal probability assessments, regarding the likely outcome of your action.

And of course if you're going to fully describe what a rule means, you have to define things in it like "lie", just as to fully describe utilitarianism you have to define "utility".