Summary Judgment vs. Motion to Dismiss: Rule 56 vs. Rule 12(b)(6) Explained

Both Rule 12(b)(6) and Rule 56 are mechanisms that can end a lawsuit before it reaches a jury. But they operate at entirely different stages of litigation and apply entirely different standards. Conflating them is one of the most common 1L errors on exams and bar prep alike.

Rule 12(b)(6) — motion to dismiss for failure to state a claim — operates at the pleading stage. It tests only whether the complaint adequately states a legally cognizable claim. The court accepts all of the plaintiff's well-pleaded factual allegations as true and asks: even if everything in this complaint is correct, does it state a claim on which relief can be granted?

Rule 56 — summary judgment — operates after discovery. It tests whether there is a genuine dispute of material fact that requires a trial to resolve. The court looks at the actual evidence — depositions, documents, affidavits — and asks: is there anything in the record that a reasonable jury could use to find for the non-moving party?

Under Federal Rule of Civil Procedure 12(b)(6), a defendant can move to dismiss a complaint before answering it. The standard comes from two Supreme Court cases: Bell Atlantic Corp. v. Twombly (2007) and Ashcroft v. Iqbal (2009).

The Twombly/Iqbal plausibility standard: a complaint must contain factual allegations that plausibly (not just conceivably) give rise to an entitlement to relief. Courts apply a two-step Iqbal analysis: (1) identify and disregard conclusory allegations that are not entitled to the assumption of truth; (2) ask whether the remaining well-pleaded factual allegations plausibly support the claim.

Key: the court does not consider evidence outside the complaint at the 12(b)(6) stage. No depositions. No affidavits. No discovery record. Just the complaint itself (and documents attached to or incorporated by it). The plaintiff's factual allegations are taken as true. The question is purely whether those facts, if true, state a valid legal claim.

If the motion is granted, the case is typically dismissed — but often with leave to amend. The plaintiff gets a chance to fix the deficient complaint rather than being barred from court entirely.

Summary judgment is available after discovery closes (though courts can permit early motions). Under Rule 56(a), summary judgment must be granted if 'there is no genuine dispute as to any material fact and the movant is entitled to judgment as a matter of law.'

The burden-shifting framework from the 'Celotex trilogy' controls how this works in practice:

Celotex Corp. v. Catrett (1986): The moving party does not have to affirmatively negate every element of the opponent's case. Instead, it can point to the absence of evidence in the record — 'the plaintiff has no evidence of causation.' The burden then shifts to the non-moving party to come forward with evidence showing a genuine dispute.

Anderson v. Liberty Lobby (1986): A dispute is 'genuine' only if the evidence is such that a reasonable jury could return a verdict for the non-moving party. Courts consider the evidence in the light most favorable to the non-moving party. 'Material' means a fact that could affect the outcome under the governing substantive law.

Matsushita Electric v. Zenith Radio (1986): The non-moving party cannot simply rest on the pleadings. They must present concrete evidence — not mere allegations — to survive summary judgment. Where the non-moving party's theory is implausible, weaker evidence is required to grant summary judgment in favor of the movant.

On exams and in practice, the critical question is always: what stage of litigation are we at, and what record does the court have?

If the defendant moves to dismiss immediately after being served with the complaint and before any discovery, that's 12(b)(6). The court is looking at the four corners of the complaint, taking all facts as true.

If discovery has happened and the defendant now points to the record and argues 'plaintiff has no evidence of X,' that's summary judgment. The court looks at whether the plaintiff has produced enough evidence for a jury to find in their favor.

A common exam trap: facts where a defendant moves at the pleading stage but cites evidence the complaint didn't allege. A 12(b)(6) motion can't rely on outside evidence — if the defendant is using discovery-stage materials, the motion should be converted to one for summary judgment (see Rule 12(d)). Many courts automatically do this conversion.