Can I give a creature First Strike in order to prevent it dealing any damage that combat?

Question

This is getting into some nitpicky corners of the rulebook.

First Strike damage and normal combat damage are dealt at separate times, and I believe there is a chance between the two resolving to play instants and other effects.

Does this mean that Swift Justice (for example) can be used to cause a creature to deal no combat damage in a turn?

1. First Strike damage is assigned and resolved (my opponent's creature does not have first strike, and therefore deals no combat damage during this step).
2. I cast Swift Justice on my opponent's creature.
3. Normal combat damage is assigned and resolved (my opponent's creature does have First Strike, and therefore deals no combat damage during this step).

Does this work if there are no creatures in combat that have First Strike normally? (i.e. Do we skip the First Strike damage step if no creatures have First Strike?)

Answer 1

Long story short, no: you can't give a creature First Strike after the first strike combat damage step in order to stop it dealing damage. It will deal its damage as soon as it gets a reasonable window of opportunity.

Here's the relevant portions of the Comprehensive Rules:

702.7b If at least one attacking or blocking creature has first strike or double strike (see rule 702.4) as the combat damage step begins, the only creatures that assign combat damage in that step are those with first strike or double strike. After that step, instead of proceeding to the end of combat step, the phase gets a second combat damage step. The only creatures that assign combat damage in that step are the remaining attackers and blockers that had neither first strike nor double strike as the first combat damage step began, as well as the remaining attackers and blockers that currently have double strike. After that step, the phase proceeds to the end of combat step.

702.7c Giving first strike to a creature without it after combat damage has already been dealt in the first combat damage step won't prevent that creature from assigning combat damage in the second combat damage step. Removing first strike from a creature after it has already dealt combat damage in the first combat damage step won't allow it to also assign combat damage in the second combat damage step (unless the creature has double strike).