Does the Rogue's Assassinate feature grant criticals on multiple attacks?

Question

Does the Rogue's Assassinate feature (auto-crit on surprised targets) allow for multiple crits if you make multiple attacks that round, either through two-weapon fighting or extra attacks gained through multiclassing?

As an example: my 3rd level Human (Variant, TWF feat) Rogue-Assassin rolls high on his stealth roll, and gets up behind his target. With two daggers, he gets 2 attacks per round if he uses his bonus action as well. Do both of these attacks qualify for Assasinate's auto-crit feature?

That is: would I do 2 criticals for

4d4+4d6+2*DEX damage

or a single critical and a non-critical for

3d4+4d6+2*DEX damage?

Additionally, if I gained the Extra Attack feature through multiclassing, would I get crits on all 3 of my attacks, or just the first one?

Answer 1

You are right for the number of critical hits. The Assassinate feature (PHB, p. 97) says:

Starting at 3rd level, you are at your deadliest when you get the drop on your enemies. You have advantage on attack rolls against any creature that hasn’t taken a turn in the combat yet. In addition, any hit you score against a creature that is surprised is a critical hit.

When an enemy is surprised, you play your full turn. If you multiclass into fighter to have Extra Attack, yes, you can have more critical hits if you hit (you have advantage on your attacks since they didn't move yet). One detail that you must not forget is that the Sneak Attack damage is applicable only once in your turn:

Once per turn, you can deal extra 1d6 damage to one creature you hit with an attack

With a level 5 fighter and a level 3 rogue with two daggers, the damage would be (assuming they all hit):

2d4+DEX (first hit) + 2d4+DEX (second hit) + 4d6 (sneak attack damage) + 2d4 (off-hand attack)

Answer 2

Yes

The definition of the Assassinate feature, from page 97 of the PHB,

any hit you score against a creature that is surprised is a critical hit

does not state that the effect only occurs once. Additionally, the definition of Surprised, on page 189

Any character or monster that doesn’t notice a threat is surprised at the start of the encounter. If you’re surprised, you can’t move or take an action on your first turn of the combat, and you can’t take a reaction until that turn ends. A member of a group can be surprised even if the other members aren’t

does not say anything about when the surprised condition ends.

---

As it seems that surprise lasts until the end of the combatant's first turn, it also seems as though the Assassinate feature should trigger for each attack made until the target is no longer surprised.