Affirmative Defenses

What It Is

An affirmative defense is a legal argument that says, in effect: “Even if everything you say is true, I still win because of [some additional legal reason].” Unlike a regular defense (which attacks your facts or legal theory), an affirmative defense introduces new matter that defeats your claim.

In § 1983 cases, affirmative defenses are powerful tools defendants use to avoid liability — and several of them are case-killers if you’re not prepared.

The Defendant’s Burden

Here’s the good news: the defendant must raise affirmative defenses in their answer to your complaint, and they bear the burden of proving them. Under Federal Rule of Civil Procedure 8(c), if the defendant doesn’t raise an affirmative defense in their answer, they generally waive it.

This means you should read the defendant’s answer carefully to see what defenses they’ve raised.

Common Affirmative Defenses in § 1983 Cases

Qualified Immunity

The most common and most devastating defense. Qualified immunity shields government officials from liability unless they violated a clearly established constitutional right. The defendant argues either (1) no constitutional violation occurred, or (2) the law wasn’t clearly established at the time.

Statute of Limitations

Your claim must be filed within the applicable statute of limitations. In § 1983 cases, the deadline is borrowed from your state’s personal injury statute — typically 2-3 years. Miss it, and your case is dead.

Heck Doctrine

Under Heck v. Humphrey, 512 U.S. 477 (1994), if winning your § 1983 case would imply that your criminal conviction was invalid, your claim is barred until the conviction is reversed. See Heck doctrine.

Absolute Immunity

Certain officials — judges, prosecutors acting in their prosecutorial capacity, legislators — have absolute immunity and cannot be sued under § 1983 for actions within their official functions, no matter how egregious.

Failure to Exhaust (Prisoners)

Under the Prison Litigation Reform Act, prisoners must exhaust all available administrative remedies (grievance procedures) before filing a § 1983 lawsuit.

Res Judicata / Collateral Estoppel

If the same issue or claim was already decided in a prior proceeding, the defendant may argue you can’t relitigate it. See collateral estoppel.

How to Respond

When the defendant raises affirmative defenses:

1. Identify which defenses actually apply — Defendants often list every conceivable defense as boilerplate. Many won’t be relevant.
2. Research the elements — Each defense has specific requirements the defendant must prove.
3. Gather contrary evidence — For qualified immunity, show the law was clearly established. For statute of limitations, argue tolling.
4. Challenge waived defenses — If a defense wasn’t raised in the answer, argue it’s waived.

Key Cases

• Heck v. Humphrey, 512 U.S. 477 (1994) — Favorable-termination requirement when § 1983 claim challenges conviction
• Harlow v. Fitzgerald, 457 U.S. 800 (1982) — Established the modern qualified immunity standard
• Gomez v. Toledo, 446 U.S. 635 (1980) — Qualified immunity is an affirmative defense; defendant bears the burden